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Sample records for memory compound ni

  1. The crystal structure and phase transitions of the magnetic shape memory compound Ni2MnGa

    International Nuclear Information System (INIS)

    Brown, P J; Crangle, J; Kanomata, T; Matsumoto, M; Neumann, K-U; Ouladdiaf, B; Ziebeck, K R A

    2002-01-01

    High resolution neutron powder diffraction and single crystal measurements on the ferromagnetic shape memory compound Ni 2 MnGa have been carried out. They enabled the sequence of transformations which take place when the unstressed, stoichiometric compound is cooled from 400 to 20 K to be established. For the first time the crystallographic structure of each of the phases which occur has been determined. At 400 K the compound has the cubic L2 1 structure, and orders ferromagnetically at T C ∼ 365 K. On cooling below ∼ 260 K a super-structure, characterized by tripling of the repeat in one of the (110) cubic directions, forms. This phase, known as the pre-martensitic phase, persists down to the structural phase transition at T M ∼ 200 K and can be described by an orthorhombic unit cell with lattice parameters a ortho = 1/√2a cubic , b ortho = 3/√2a cubic , c ortho = a cubic and space group Pnnm. Below T M the compound has a related orthorhombic super-cell with b ortho ∼ 7/√2a cubic , which can be described within the same space group. The new modulation appears abruptly at T M and remains stable down to at least 20 K

  2. Magnetic and structural properties of the magnetic shape memory compound Ni2Mn1.48Sb0.52

    International Nuclear Information System (INIS)

    Brown, P J; Gandy, A P; Neumann, K U; Sheikh, A; Ziebeck, K R A; Ishida, K; Oikawa, K; Ito, W; Kainuma, R; Kanomata, T; Ouladdiaf, B

    2010-01-01

    Magnetization and high resolution neutron powder diffraction measurements on the magnetic shape memory compound Ni 2 Mn 1.48 Sb 0.52 have confirmed that it is ferromagnetic below 350 K and undergoes a structural phase transition at T M ∼310 K. The high temperature phase has the cubic L2 1 structure with a = 5.958 A, with the excess manganese atoms occupying the 4(b) Sb sites. In the cubic phase above ∼310 K the manganese moments are ferromagnetically aligned. The magnetic moment at the 4(a) site is 1.57(12) μ B and it is almost zero (0.15(9) μ B ) at the 4(b) site. The low temperature orthorhombic phase which is only fully established below 50 K has the space group Pmma with a cell related to the cubic one by a Bain transformation a orth = (a cub + b cub )/2; b orth = c cub and c orth = (a cub - b cub ). The change in cell volume is ∼2.5%. The spontaneous magnetization of samples cooled in fields less than 0.5 T decreases at temperatures below T M and at 2 K the magnetic moment per formula unit in fields up to 5.5 T is 2.01(5) μ B . Neutron diffraction patterns obtained below ∼132 K gave evidence for a weak incommensurate magnetic modulation with propagation vector (2/3, 1/3, 0).

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

    Czech Academy of Sciences Publication Activity Database

    Holec, David; Bojda, Ondřej; Dlouhý, Antonín

    2008-01-01

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

  4. Crystal structure of the martensite phase in the ferromagnetic shape memory compound Ni2MnGa studied by electron diffraction

    International Nuclear Information System (INIS)

    Fukuda, Takashi; Kushida, Hiroaki; Todai, Mitsuharu; Kakeshita, Tomoyuki; Mori, Hirotaro

    2009-01-01

    The electron diffraction patterns of Ni 2 MnGa show six satellites at ±q M , ±2q M and ±3q M , with q M = 0.427(5) g 22 -bar 0 between fundamental reflections in the martensite phase, and two satellites at ±q I , with q I = 0.340(5) g 22 -bar 0 in the intermediate phase, meaning that these phases have incommensurate structures. In addition, the diffraction pattern of the intermediate phase continuously changes to that of the parent phase via the X-phase, suggesting the existence of a multicritical phenomenon.

  5. The influence of atomic order on the magnetic and structural properties of the ferromagnetic shape memory compound Ni sub 2 MnGa

    CERN Document Server

    Kreissl, M; Stephens, T; Ziebeck, K R A

    2003-01-01

    The effect of atomic order on the martensitic phase transition and magnetic properties of stoichiometric Ni sub 2 MnGa has been investigated in a sample quenched from 1000 deg C. Magnetization, resistivity and x-ray diffraction measurements indicate that the structural phase transition occurs at approx 103 K, substantially lower than the value reported for samples quenched from 800 deg C and ordered in the Heusler L2 sub 1 structure. A small reduction in the ferromagnetic moment was also observed, although the Curie temperature remained largely unaffected. The electronic Sommerfeld coefficient obtained from heat capacity measurements is enhanced but smaller than that observed for the 800 deg C quenched sample. The results are consistent with band structure calculations and the electronic changes brought about by atomic disorder.

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

    International Nuclear Information System (INIS)

    Holec, D.; Bojda, O.; Dlouhy, A.

    2008-01-01

    Non-uniform distributions of Ni 4 Ti 3 precipitate crystallographic variants are investigated in a Ni-rich NiTi shape memory alloy after aging, assisted by external stress. A finite-element method model is presented that considers the elastic anisotropy of the B2 parent phase and also mutual misorientations of grains in a polycrystalline sample. On loading by the external stress, the stress is redistributed in the microstructure and the precipitation of some Ni 4 Ti 3 crystallographic variants becomes distinctly favorable in grain boundary regions since these variant configurations minimize the elastic interaction energy. The volume fraction of the affected grain boundary regions is calculated and the numerical results are compared with the data obtained by differential scanning calorimetry and transmission electron microscopy

  7. Pseudo-elasticity and shape memory effect on the TiNiCoV alloy

    International Nuclear Information System (INIS)

    Hsu, S.E.; Yeh, M.T.; Hsu, I.C.; Chang, S.K.; Dai, Y.C.; Wang, J.Y.

    2000-01-01

    Unlike most of the structural intermetallic compound, TiNi is an exceptional case of inherent ductility. Besides its amusing behavior of high damping capacity due to martensitic transformation, the duel properties of shape memory and pseudo-elasticity co-exhibited in the same V and Co-modified TiNi-SMA at various temperature will attract another attention in modern manufacturing technology. The objective of this paper is to investigate the pseudo-elasticity and strain rate effect on TiNiCoV-SMA. The presence of dual behavior of super-elasticity and shape memory effect is technological significant for application of advanced materials on the structural component. An illustration of application of TiNiCoV shape memory alloy on the face of golf club head will be presented in this paper. (orig.)

  8. Mechanical and shape memory properties of ferromagnetic Ni2MnGa sputter-deposited films

    Science.gov (United States)

    Ohtsuka, M.; Matsumoto, M.; Itagaki, K.

    2003-10-01

    The ternary intermetallic compound Ni2MnGa is an intelligent material, which has a shape memory effect and a ferromagnetic property. Use of shape memory alloy films for an actuator of micro machines is very attractive because of its large recovery force. The data of mechanical and shape memory properties of the films are required to use for the actuator. The purpose of this study is to investigate the effects of fabrication conditions and to clarify the relationships between these properties and fabrication conditions of the Ni{2}MnGa films. The Ni{2}MnGa films were deposited with a radio-frequency magnetron sputtering apparatus using a Ni{50}Mn{25}Ga{25} or Ni{52}Mn{24}Ga{24} target. After deposition, the films were annealed at 873sim 1173 K. The asdeposited films were crystalline and had columnar grains. After the heat treatment, the grains widened and the grain boundary became indistinct with increasing heat treatment temperature. MnO and Ni{3} (Mn, Ga) precipitations were observed in the heat-treated films. The mechanical properties of the films were measured by the nanoindentation method. Hardness and elastic modulus of as-deposited films were larger than those of arcmelted bulk alloys. The hardness of the films was affected by the composition, crystal structure, microstructure and precipitation, etc. The elastic modulus of the films was also changed with the heat treatment conditions. The heat-treated films showed a thermal two-way shape memory effect.

  9. Ti-Ni-based shape memory alloys as smart materials

    International Nuclear Information System (INIS)

    Otsuka, K.; Xu, Y.; Ren, X.

    2003-01-01

    Smart materials consist of three principal materials, ferroelectrics, shape memory alloys (SMA) and electro-active polymers (EAP). Among these SMAs, especially Ti-Ni-based alloys are important, since only they can provide large recoverable strains and high recovery stress. In the present paper the unique characteristics of Ti-Ni-based shape memory alloys are reviewed on an up-to-date basis with the aim of their applications to smart materials and structures. (orig.)

  10. Memory and Perfection in Ferroelastic Inclusion Compounds

    International Nuclear Information System (INIS)

    Hollingsworth, M.; Peterson, M.; Rush, J.; Brown, M.; Abel, M.; Black, A.; Dudley, M.; Raghothamachar, B.; Werner-Zwanziger, U.

    2005-01-01

    In a series of ferroelastic urea inclusion compounds (UICs), in which domain reorientation occurs upon application of an external anisotropic force, introduction of a relaxive impurity that disrupts a specific hydrogen-bonding network transforms a plastic (irreversible) domain-switching process into one that exhibits a striking memory effect and 'rubber-like behavior', a form of pseudoelasticity. As expected for a highly cooperative process, the ferroelastic response to the impurity concentration exhibits a critical threshold. Through synchrotron white-beam X-ray topography (SWBXT) of crystals under stress, videomicroscopy of spontaneous repair during crystal growth, acoustomechanical relaxation of daughter domains, kinetic measurements of spontaneous domain reversion, and solid-state 2 H NMR of labeled guests, this work shows how relaxive impurities lower the barrier to domain switching and how differences in perfection between mother and daughter domains provide the driving force for the memory effects. Although the interfacial effects implicated here are different from the volume effects that operate in certain shape memory materials, the twinning and defect phenomena responsible for the rubber-like behavior and memory effects should be generally applicable to domain switching in ferroelastic and ferroelectric crystals and to other solid-state processes

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

    International Nuclear Information System (INIS)

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

    1990-01-01

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

  12. Large magnetocaloric effect of GdNiAl2 compound

    International Nuclear Information System (INIS)

    Dembele, S.N.; Ma, Z.; Shang, Y.F.; Fu, H.; Balfour, E.A.; Hadimani, R.L.; Jiles, D.C.; Teng, B.H.; Luo, Y.

    2015-01-01

    This paper presents the structure, magnetic properties, and magnetocaloric effect of the polycrystalline compound GdNiAl 2 . Powder X-ray diffraction (XRD) measurement and Rietveld refinement revealed that GdNiAl 2 alloy is CuMgAl 2 -type phase structure with about 1 wt% GdNi 2 Al 3 secondary phase. Magnetic measurements suggest that the compound is ferromagnetic and undergoes a second-order phase transition near 28 K. The maximum value of magnetic entropy change reaches 16.0 J/kg K for an applied magnetic field change of 0–50 kOe and the relative cooling power was 6.4×10 2 J/kg. It is a promising candidate as a magnetocaloric material working near liquid hydrogen temperature (~20 K) exhibiting large relative cooling power. - Highlights: • Preferred orientation with axis of [010] was found in the GdNiAl 2 compound. • The ΔS Mmax and the RCP are 16.0 J/kg K and 640 J/kg, respectively, for ΔH=50 kOe. • Relative low rare earth content in GdNiAl 2 comparing with other candidates

  13. Antiferromagnetic ordering of Er2NiSi3 compound

    International Nuclear Information System (INIS)

    Pakhira, Santanu; Mazumdar, Chandan; Ranganathan, R.

    2014-01-01

    Ternary intermetallics of the stoichiometric composition R 2 TX 3 , where, R = rare earth element, T = d-electron transition metal and X= p-electron element, crystallizes in hexagonal A1B 2 type crystal structure with space group P6/mmm. We report here the synthesis and basic magnetic properties of the compound Er 2 NiSi 3 . Paramagnetic to antiferromagnetic phase change occurs below 5.4 K for this compound. (author)

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

    Science.gov (United States)

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

    2018-03-01

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

  15. Microstructural evolution of Ni40Zr60 alloy during early stage of mechanical alloying of intermetallic compounds NiZr2 and Ni11Zr9

    International Nuclear Information System (INIS)

    Lee Peeyew; Koch, C.C.

    1994-01-01

    The microstructural change of Ni 40 Zr 60 alloy during mechanical alloying of mixtures of the intermetallic compounds NiZr 2 and Ni 11 Zr 9 has been studied by transmission electron microscopy. A specific ''cauliflower'' phase was formed during early stage of mechanical alloying process. It is suggested that the solid state reaction between intermetallic compounds NiZr 2 and Ni 11 Zr 9 is not the only origin for the formation of the ''cauliflower'' phase. ((orig.))

  16. Precipitation-induced of partial annealing of Ni-rich NiTi shape memory alloy

    Science.gov (United States)

    Nashrudin, Muhammad Naqib; Mahmud, Abdus Samad; Mohamad, Hishamiakim

    2018-05-01

    NiTi shape memory alloy behavior is very sensitive to alloy composition and heat treatment processes. Thermomechanical behavior of near-equiatomic alloy is normally enhanced by partial anneal of a cold-worked specimen. The shape memory behavior of Ni-rich alloy can be enhanced by ageing precipitation. This work studied the effect of simultaneous partial annealing and ageing precipitation of a Ni-rich cold drawn Ti-50.9at%Ni wire towards martensite phase transformation behavior. Ageing treatment of a non-cold worked specimen was also done for comparison. It was found that the increase of heat treatment temperature caused the forward transformation stress to decrease for the cold worked and non-cold worked specimens. Strain recovery on the reverse transformation of the cold worked wire improved compared to the non-cold worked wire as the temperature increased.

  17. Precipitation of Ni4Ti3-variants in a polycrystalline Ni-rich NiTi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Bojda, Ondřej; Eggeler, G.; Dlouhý, Antonín

    2005-01-01

    Roč. 53, č. 1 (2005), s. 99-104 ISSN 1359-6462 R&D Projects: GA ČR(CZ) GA106/05/0918 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi shape memory alloys * Ni4Ti3 precipitation * Transmission electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.228, year: 2005

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

    Science.gov (United States)

    Fann, Kaung-Jau; Su, Jhe-Yung

    2018-03-01

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

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

    International Nuclear Information System (INIS)

    Duan Yuangang

    1995-01-01

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

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

    International Nuclear Information System (INIS)

    Schlossmacher, P.; Stober, T.

    1995-01-01

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

  1. Elastic properties of LaSnxNi5-x compounds

    International Nuclear Information System (INIS)

    Yeheskel, O.; Nattrass, C.E.; Leisure, R.G.; Jacob, I.; Bowman, R.C. Jr.

    2004-01-01

    Ultrasonic methods were used to measure the room-temperature elastic moduli of polycrystalline LaSn x Ni 5-x compounds for 0≤x≤0.5. These materials are of great importance for their hydrogen storage properties. The samples, prepared by a hot isostatic pressing method, had near-theoretical densities with calculated porosities ranging from 0 to 1.5%. The porosity-corrected moduli decreased with increasing x. Poisson's ratio was approximately constant at 0.314 for all the compounds. The Debye temperature, calculated from the RT polycrystalline moduli, decreased from 359 to 344 K as x increased from 0 to 0.5. The results were used to calculate the elastic interaction energy of an interstitial hydrogen atom with the strain fields of all the other interstitial hydrogen. This energy was in turn used to calculate the critical temperature below which phase separation occurs in LaM x Ni 5-x H y compounds (M=Sn or Al). It was found that the critical temperature decreases with increasing x, confirming in a more general way a conclusion drawn for a specific case from earlier thermodynamic measurements. It is suggested that the lowering of the critical temperature plays a role in limiting the width of the plateaus in pressure-composition isotherms for the two-phase regions of these compounds. This suggestion implies a relation between the elastic properties and the maximum hydrogen capacity

  2. Thermomechanical model for NiTi shape memory wires

    International Nuclear Information System (INIS)

    Frost, M; Sedlák, P; Sippola, M; Šittner, P

    2010-01-01

    A simple one-dimensional rate-independent model is proposed. It is able to capture responses of a NiTi shape memory alloy wire element to mechanical and thermal loadings. Since the model takes into account martensitic phase transformation as well as deformation processes in the martensite, both shape memory effects and pseudoelasticity can be simulated. The model introduces non-hysteretic transformation strain. Particular attention was paid to description of partial loading cycles. By changing the input parameters the model can be adapted to various types of NiTi-based materials. The model was implemented in the finite element code Abaqus as a User routine and several simulations were performed to validate the implementation

  3. Effect of cooling rate on the phase transformation behavior and mechanical properties of Ni-rich NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Motemani, Y. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Nili-Ahmadabadi, M. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, 14395-731 Tehran (Iran, Islamic Republic of); Tan, M.J. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798 (Singapore)], E-mail: mmjtan@ntu.edu.sg; Bornapour, M.; Rayagan, Sh. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, 14395-731 Tehran (Iran, Islamic Republic of)

    2009-02-05

    TiNi alloy is a well-known shape memory alloy and has been widely used for bio-medical, mechanical and electrical applications. In this study, a Ni-rich NiTi alloy was prepared by vacuum arc melting in a water-cooled copper crucible. Three samples of this alloy were heated to 1000 deg. C and cooled in three media: furnace, water, and dry-ice bath. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), hardness measurement and tensile test were carried out to investigate the effect of cooling rate on transformation temperature and mechanical properties. The results show that Ni{sub 3}Ti intermetallic compounds have a great influence on martensitic phase transformation temperature. These tests clearly showed the correlation between cooling rate and properties of the alloy.

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

    OpenAIRE

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

    2017-01-01

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

  5. Thermal processing of polycrystalline NiTi shape memory alloys

    International Nuclear Information System (INIS)

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

    2005-01-01

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

  6. Shape memory properties in NiTi alloys

    International Nuclear Information System (INIS)

    Airoldi, G.; Vicentini, B.; Ranucci, T.; Rivolta, B.

    1991-01-01

    Mechanical properties of shape memory NiTi alloys are here examined in the frame of literature's results. The operating temperature respect to the intrinsic transformation temperatures explains thoroughly the different stress-strain behaviour, ascribed to different deformation mechanisms acting and to their interplay. Attention is moreover paid to the stress-strain behaviour consequent to a different physical state (martensite phase or parent phase), obtained within the hysteresis cycle, at the same temperature. Evidence of oriented variants, selected by the applied stress, is also given

  7. Phase transformation and precipitation in aged Ti-Ni-Hf high-temperature shape memory alloys

    International Nuclear Information System (INIS)

    Meng, X.L.; Cai, W.; Zheng, Y.F.; Zhao, L.C.

    2006-01-01

    More attention has been paid to ternary Ti-Ni-Hf high-temperature shape memory alloys (SMAs) due to their high phase transformation temperatures, good thermal stability and low cost. However, the Ti-Ni-Hf alloys have been found to have low ductility and only about 3% shape memory effect and these have hampered their applications. It is well known that there are three methods to improve the shape memory properties of high-temperature SMAs: (a) cold rolling + annealing; (b) adding another element to the alloy; (c) aging. These methods are not suitable to improve the properties of Ti-Ni-Hf alloys. In this paper, a method of conditioning Ni-rich Ti-Ni-Hf alloys as high-temperature SMAs by aging is presented. For Ni-rich Ti 80-x Ni x Hf 20 alloys (numbers indicate at.%) the phase transformation temperatures are on average increased by more than 100 K by aging at 823 K for 2 h. Especially for those alloys with Ni contents less than 50.6 at.%, the martensitic transformation start temperatures (M s ) are higher than 473 K after aging. Transmission electron microscopy shows the presence of (Ti + Hf) 3 Ni 4 precipitates after aging. Compared with the precipitation of Ti 3 Ni 4 particles in Ni-rich Ti-Ni alloys, the precipitation of (Ti + Hf) 3 Ni 4 particles in Ni-rich Ti-Ni-Hf alloys needs higher temperatures and longer times

  8. Magnetic properties of two new compounds: Pr2Ni3Si5 and Ho2Ni3Si5

    International Nuclear Information System (INIS)

    Mazumdar, C.; Padalia, B.D.; Godart, C.

    1994-01-01

    Formation of two more new materials, Pr 2 Ni 3 Si 5 and Ho 2 Ni 3 Si 5 , of the series, R 2 Ni 3 Si 5 (R = rare earth and Y) and their magnetic properties are reported here. These materials crystallize in the orthorhombic U 2 Co 3 Si 5 -type structure (space group Ibam). Magnetic susceptibility measurement in the temperature range 5 K--300 K show that the compound Pr 2 Ni 3 Si 5 order antiferromagnetically at T N ∼ 8.5 K and Ho 2 Ni 3 Si 5 at ∼ 6 K. Considering T N (Gd 2 Ni 3 Si 5 ) ∼ 15 K, T N (Pr 2 Ni 3 Si 5 ) ∼ 8.5 K is rather high. The magnetic susceptibility of both of the materials, in the paramagnetic state, follows a Curie-Weiss law with effective moment close to that of the corresponding free trivalent rare earth ion

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

    International Nuclear Information System (INIS)

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

    2007-01-01

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

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

    International Nuclear Information System (INIS)

    Yang, Z.Q.; Schryvers, D.

    2008-01-01

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

  11. NiTiCu/AlN/NiTiCu shape memory thin film heterostructures for vibration damping in MEMS

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Navjot; Kaur, Davinder, E-mail: dkaurfph@iitr.ernet.in

    2014-03-25

    Highlights: • Fabrication of NiTiCu/AlN/NiTiCu heterostructure using dc/rf magnetron sputtering. • Exhibits highest hardness (38 GPa) and elastic modulus (187 GPa). • Enhanced dissipation of mechanical energy (E{sub d} = 5.7 N J). • High damping capacity (0.052) and figure of merit (∼0.62). • Can be applied for vibration damping in MEMS. -- Abstract: Shape memory alloy (NiTiCu) thin films coupled with piezoelectric AlN layer produce an intelligent material for vibration damping. In the present study pure NiTiCu, NiTiCu/AlN and NiTiCu/AlN/NiTiCu heterostructures have been deposited on Si substrate using magnetron sputtering technique. By the use of the interfaces and shape memory effect provided by NiTiCu layers, the damping capacity can be increased along with increase in stiffness and mechanical hardness. The heterostructures were characterized in terms of structural, electrical, morphological and mechanical properties by X-ray diffraction (XRD), four probe resistivity method, atomic force microscopy, field emission scanning electron microscopy, and nanoindentation. The NiTiCu/AlN/NiTiCu heterostructure exhibit enhanced mechanical and damping properties as compared to NiTiCu/AlN and pure NiTiCu. This enhancement in hardness and damping of the heterostructure could be attributed to the shape memory effect of NiTiCu, intrinsic piezoelectricity of AlN and increased number of interfaces in heterostructure that help in dissipation of mechanical vibrations. The findings of this work provide additional impetus for the application of these heterostructures in emerging fields of nanotechnology and microelectro mechanical (MEMS) devices.

  12. NiTiCu/AlN/NiTiCu shape memory thin film heterostructures for vibration damping in MEMS

    International Nuclear Information System (INIS)

    Kaur, Navjot; Kaur, Davinder

    2014-01-01

    Highlights: • Fabrication of NiTiCu/AlN/NiTiCu heterostructure using dc/rf magnetron sputtering. • Exhibits highest hardness (38 GPa) and elastic modulus (187 GPa). • Enhanced dissipation of mechanical energy (E d = 5.7 N J). • High damping capacity (0.052) and figure of merit (∼0.62). • Can be applied for vibration damping in MEMS. -- Abstract: Shape memory alloy (NiTiCu) thin films coupled with piezoelectric AlN layer produce an intelligent material for vibration damping. In the present study pure NiTiCu, NiTiCu/AlN and NiTiCu/AlN/NiTiCu heterostructures have been deposited on Si substrate using magnetron sputtering technique. By the use of the interfaces and shape memory effect provided by NiTiCu layers, the damping capacity can be increased along with increase in stiffness and mechanical hardness. The heterostructures were characterized in terms of structural, electrical, morphological and mechanical properties by X-ray diffraction (XRD), four probe resistivity method, atomic force microscopy, field emission scanning electron microscopy, and nanoindentation. The NiTiCu/AlN/NiTiCu heterostructure exhibit enhanced mechanical and damping properties as compared to NiTiCu/AlN and pure NiTiCu. This enhancement in hardness and damping of the heterostructure could be attributed to the shape memory effect of NiTiCu, intrinsic piezoelectricity of AlN and increased number of interfaces in heterostructure that help in dissipation of mechanical vibrations. The findings of this work provide additional impetus for the application of these heterostructures in emerging fields of nanotechnology and microelectro mechanical (MEMS) devices

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

    International Nuclear Information System (INIS)

    Hattori, Shuji; Fujisawa, Seiji; Owa, Tomonobu

    2007-01-01

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

  14. Cyclic deformation of NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Liu Yong; Van Humbeeck, J.; Xie Zeliang

    1999-01-01

    Recently, there is an increasing interest in applying the high damping capacity of shape memory alloys (SMAs). The purpose is to explore the feasibility of those materials for the protection of buildings and other civil constructions as a result of earthquake damages. So far, few experimental results have been reported concerning the mechanical cyclic behaviour of SMAs in their martensitic state (ferroelastic). In the present work, the experimental results on the mechanical behaviour of martensitic NiTi SMAs under tension-compression cyclic deformation up to strains of ±4% are summarized with major attention to the damping capacity, characteristic stresses and strains as a function of deformation cycles. Effect of strain rate, strain amplitude and annealing condition on the martensite damping is summarized. Explanation of the cyclic hardening and cyclic softening phenomenon is proposed based on TEM observations. (orig.)

  15. Ab-initio thermodynamic and elastic properties of AlNi and AlNi3 intermetallic compounds

    Science.gov (United States)

    Yalameha, Shahram; Vaez, Aminollah

    2018-04-01

    In this paper, thermodynamic and elastic properties of the AlNi and AlNi3 were investigated using density functional theory (DFT). The full-potential linearized augmented plane-wave (APW) in the framework of the generalized gradient approximation as used as implemented in the Wien2k package. The temperature dependence of thermal expansion coefficient, bulk modulus and heat capacity in a wide range of temperature (0-1600 K) were investigated. The calculated elastic properties of the compounds show that both intermetallic compounds of AlNi and AlNi3 have surprisingly negative Poisson’s ratio (NPR). The results were compared with other experimental and computational data.

  16. DO22-(Cu,Ni)3Sn intermetallic compound nanolayer formed in Cu/Sn-nanolayer/Ni structures

    International Nuclear Information System (INIS)

    Liu Lilin; Huang, Haiyou; Fu Ran; Liu Deming; Zhang Tongyi

    2009-01-01

    The present work conducts crystal characterization by High Resolution Transmission Electron Microscopy (HRTEM) on Cu/Sn-nanolayer/Ni sandwich structures associated with the use of Energy Dispersive X-ray (EDX) analysis. The results show that DO 22 -(Cu,Ni) 3 Sn intermetallic compound (IMC) ordered structure is formed in the sandwich structures at the as-electrodeposited state. The formed DO 22 -(Cu,Ni) 3 Sn IMC is a homogeneous layer with a thickness about 10 nm. The DO 22 -(Cu,Ni) 3 Sn IMC nanolayer is stable during annealing at 250 deg. C for 810 min. The formation and stabilization of the metastable DO 22 -(Cu,Ni) 3 Sn IMC nanolayer are attributed to the less strain energy induced by lattice mismatch between the DO 22 IMC and fcc Cu crystals in comparison with that between the equilibrium DO 3 IMC and fcc Cu crystals.

  17. Fabrication and thermoelectric properties of fine-grained TiNiSn compounds

    International Nuclear Information System (INIS)

    Zou Minmin; Li Jingfeng; Du Bing; Liu Dawei; Kita, Takuji

    2009-01-01

    Nearly single-phased TiNiSn half-Heusler compound thermoelectric materials were synthesized by combining mechanical alloying (MA) and spark plasma sintering (SPS) in order to reduce its thermal conductivity by refining the grain sizes. Although TiNiSn compound powders were not synthesized directly via MA, dense bulk samples of TiNiSn compound were obtained by the subsequent SPS treatment. It was found that an excessive Ti addition relative to the TiNiSn stoichiometry is effective in increasing the phase purity of TiNiSn half-Heusler phase in the bulk samples, by compensating for the Ti loss caused by the oxidation of Ti powders and MA processing. The maximum power factor value obtained in the Ti-compensated sample is 1720 μW m -1 K -2 at 685 K. A relatively high ZT value of 0.32 is achieved at 785 K for the present undoped TiNiSn compound polycrystals. - Graphical abstract: Nearly single-phased TiNiSn-based half-Heusler compound polycrystalline materials with fine grains were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS). A high ZT value for undoped TiNiSn was obtained because of the reduced thermal conductivity.

  18. Solution-processed flexible NiO resistive random access memory device

    Science.gov (United States)

    Kim, Soo-Jung; Lee, Heon; Hong, Sung-Hoon

    2018-04-01

    Non-volatile memories (NVMs) using nanocrystals (NCs) as active materials can be applied to soft electronic devices requiring a low-temperature process because NCs do not require a heat treatment process for crystallization. In addition, memory devices can be implemented simply by using a patterning technique using a solution process. In this study, a flexible NiO ReRAM device was fabricated using a simple NC patterning method that controls the capillary force and dewetting of a NiO NC solution at low temperature. The switching behavior of a NiO NC based memory was clearly observed by conductive atomic force microscopy (c-AFM).

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

    Science.gov (United States)

    Miyazaki, Shuichi

    2017-12-01

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

  20. Developing prospects of NiAlMn high temperature shape memory alloy

    International Nuclear Information System (INIS)

    Zou Min

    1999-01-01

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

  1. Neutron diffraction studies of Ho1-xYxNi2B2C compounds

    DEFF Research Database (Denmark)

    Chang, L.J.; Tomy, C.V.; Paul, D.M.K.

    1996-01-01

    Neutron diffraction measurements have been carried out to investigate the nature of magnetic ordering in Ho(1-x)Y(x)Ni(2)B(2)C (x = 0, 0.1 and 0.2) compounds. HoNi(2)B(2)C shows a complex type of magnetic ordering below the superconducting transition, with a commensurate antiferromagnetic ordering...

  2. Effect of adding Si on shape memory effect in Co-Ni alloy system

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Weimin [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China); Liu Yan [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Jiang Bohong [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)]. E-mail: bhjiang@sjtu.edu.cn; Zhou Pingnan [School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2006-11-25

    In this paper, the effect of adding Si to Co-31.5 mass% Ni alloys on fcc-hcp martensitic transformation is investigated. The Co-Ni-Si ternary alloys with different amount of Si from 1 to 5 mass% were prepared. The stacking fault probability of Co-Ni-Si polycrystalline alloys were determined by X-ray diffraction profile analysis and compared with the binary Co-Ni alloy. The results show that the stacking fault probability of the fcc phase of alloys increases with increasing Si content. The effect of Si on phase transformation and shape memory behavior is evaluated. The experimental results show that both the critical strength and the shape memory effect of the ternary alloys will increase by the addition of Si. The improvement mechanism of the shape memory effect by adding Si to binary Co-Ni alloys is discussed.

  3. Effect of ageing temperatures on pseudoelasticity of Ni-rich NiTi shape memory alloy

    Science.gov (United States)

    Mohamad, Hishamiakim; Mahmud, Abdus Samad; Nashrudin, Muhammad Naqib; Razali, Muhammad Fauzinizam

    2018-05-01

    The shape memory behavior of NiTi alloy is very sensitive to alloy composition and heat treatments, particularly annealing and ageing. This paper analysed the effect of ageing towards the thermomechanical behaviour of Ti-51at%Ni wire. The analysis focused on the effect of ageing at the different temperature on thermal transformation sequence and tensile deformation behaviour with respect to the recoverability of the alloy. It was found that B2-R transformation peak appeared in the differential scanning calorimetry (DSC) measurement when the alloys were aged at the temperature between 400°C to 475°C for 30 minutes. Further ageing at 500°C to 550°C yielded two stage transformation, B2-R-B19' in cooling. All aged wires exhibited good pseudoelastic behaviour when deformed at room temperature and yielded below 1% residual strain upon unloading. Ageing at 450°C resulted the smallest unrecovered strain of about 0.4%.

  4. Confining jackets for concrete cylinders using NiTiNb and NiTi shape memory alloy wires

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Eunsoo; Yoon, Soon-Jong [Department of Civil Engineering, Hongik University, Seoul 121-791 (Korea, Republic of); Nam, Tae-Hyun [School of Materials Science and Engineering and ERI, Gyeongsang National University, Jinju, Gyeongnam 600-701 (Korea, Republic of); Cho, Sun-Kyu [School of Civil Engineering, Seoul National University of Technology, Seoul 139-743 (Korea, Republic of); Park, Joonam, E-mail: eunsoochoi@hongik.ac.k [Department of Railroad Structure Research, Korea Railroad Research Institute, Uiwang 437-050, Korea (Korea, Republic of)

    2010-05-01

    This study used prestrained NiTiNb and NiTi shape memory alloy (SMA) wires to confine concrete cylinders. The recovery stress of the wires was measured with respect to the maximal prestrain of the wires. SMA wires were preelongated during the manufacturing process and then wrapped around concrete cylinders of 150 mmx300 mm ({phi}xL). Unconfined concrete cylinders were tested for compressive strength and the results were compared to those of cylinders confined by SMA wires. NiTiNb SMA wires increased the compressive strength and ductility of the cylinders due to the confining effect. NiTiNb wires were found to be more effective in increasing the peak strength of the cylinders and dissipating energy than NiTi wires. This study showed the potential of the proposed method to retrofit reinforced concrete columns using SMA wires to protect them from earthquakes.

  5. 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.

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

    National Research Council Canada - National Science Library

    Chung, Kohn C

    2006-01-01

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

  7. Compound words prompt arbitrary semantic associations in conceptual memory

    Directory of Open Access Journals (Sweden)

    Bastien eBoutonnet

    2014-03-01

    Full Text Available Linguistic relativity theory has received empirical support in domains such as colour perception and object categorisation. It is unknown however, whether relations between words idiosyncratic to language impact nonverbal representations and conceptualisations. For instance, would one consider the concepts of horse and sea as related were it not for the existence of the compound seahorse? Here, we investigated such arbitrary conceptual relationships using a non-linguistic picture relatedness task in participants undergoing event-related brain potential recordings. Picture pairs arbitrarily related because of a compound and presented in the compound order elicited N400 amplitudes similar to unrelated pairs. Surprisingly, however, pictures presented in the reverse order (as in the sequence horse – sea reduced N400 amplitudes significantly, demonstrating the existence of a link in memory between these two concepts otherwise unrelated. These results break new ground in the domain of linguistic relativity by revealing predicted semantic associations driven by lexical relations intrinsic to language.

  8. Interfacial reaction of Ni{sub 3}Sn{sub 4} intermetallic compound in Ni/SnAg solder/Ni system under thermomigration

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yi-Shan; Yang, Chia-Jung; Ouyang, Fan-Yi, E-mail: fyouyang@ess.nthu.edu.tw

    2016-07-25

    The growth of Ni{sub 3}Sn{sub 4} intermetallic compound (IMC) between liquid–solid interface in micro-scale Ni/SnAg/Ni system was investigated under a temperature gradient of 160 °C/cm at 260 °C on a hot plate. In contrast to a symmetrical growth of Ni{sub 3}Sn{sub 4} on both interfaces under isothermally annealed at 260 °C, the interfacial Ni{sub 3}Sn{sub 4} IMC exhibited asymmetric growth under a temperature gradient; the growth of Ni{sub 3}Sn{sub 4} at cold interface was faster than that at hot side because of temperature gradient induced mass migration of Ni atoms from the hot end toward the cold end. It was found that two-stage growth behavior of Ni{sub 3}Sn{sub 4} IMC under a temperature gradient. A growth model was established and growth kinetic analysis suggested that the chemical potential gradient controlled the growth of Ni{sub 3}Sn{sub 4} at stage I (0–120 min) whereas the dynamic equilibrium between chemical potential gradient and temperature gradient forces was attained at the hot end at stage II (120–210 min). When dynamic equilibrium was achieved at 260 °C, the critical length-temperature gradient product at the hot end was experimentally estimated to be 489.18 μm × °C/cm and the moving velocity of Ni{sub 3}Sn{sub 4} interface due to Ni consumption was calculated to be 0.134 μm/h. The molar heat of transport (Q*) of Ni atoms in molten SnAg solder was calculated to be +0.76 kJ/mol. - Highlights: • Interfacial reaction in Ni/SnAg solder/Ni system under thermal gradient. • Growth rate of Ni{sub 3}Sn{sub 4} at cold end is faster than that at hot end. • Critical length-temperature gradient product at hot end is 489.2 μm°C/cm at 260 °C. • Velocity of Ni{sub 3}Sn{sub 4} moving interface is 0.134 μm/h during dynamic equilibrium. • Molar heat of transport (Q*) of Ni in molten SnAg was +0.76 kJ/mol.

  9. A Review of Selective Laser Melted NiTi Shape Memory Alloy

    Science.gov (United States)

    Khoo, Zhong Xun; Shen, Yu Fang

    2018-01-01

    NiTi shape memory alloys (SMAs) have the best combination of properties among the different SMAs. However, the limitations of conventional manufacturing processes and the poor manufacturability of NiTi have critically limited its full potential applicability. Thus, additive manufacturing, commonly known as 3D printing, has the potential to be a solution in fabricating complex NiTi smart structures. Recently, a number of studies on Selective Laser Melting (SLM) of NiTi were conducted to explore the various aspects of SLM-produced NiTi. Compared to producing conventional metals through the SLM process, the fabrication of NiTi SMA is much more challenging. Not only do the produced parts require a high density that leads to good mechanical properties, strict composition control is needed as well for the SLM NiTi to possess suitable phase transformation characteristics. Additionally, obtaining a good shape memory effect from the SLM NiTi samples is another challenging task that requires further understanding. This paper presents the results of the effects of energy density and SLM process parameters on the properties of SLM NiTi. Its shape memory properties and potential applications were then reviewed and discussed. PMID:29596320

  10. Site determination of Ni atoms in Cu-Al-Ni shape memory alloys by electron channelling enhanced microanalysis

    International Nuclear Information System (INIS)

    Nakata, Yoshiyuki; Tadaki, Tsugio; Shimizu, Ken-ichi

    1990-01-01

    The crystallographic site of Ni atoms in the parent phase of differently heat-treated Cu-28.6Al-3.7Ni (at.%) shape memory alloys has been examined by electron channelling enhanced microanalysis (ALCHEMI) in order to clarify effects of heat-treatments on the Ni atom site and M s temperature. The heat-treatments were as follows: (a) Quenching into a 10% NaOH solution at 263 K, (b) Quenching into hot water at 363 K and (c) Aging at 523 K for 3.6 ks after treatment (b). The M s temperatures of specimens (a), (b) and (c) were 158, 185 and 259 K, respectively, increasing with lowering quenching rate or aging. ALCHEMI revealed that Ni atoms occupied an identical site in all the three kinds of specimens: The Ni atoms were located at the nearest neighbor sites around Al atoms. This preferential occupation of Ni atoms was attributed to the strong binding force between Ni and Al atoms. Thus, the change in M s temperature due to different heat-treatments was not directly related to the crystallographic site of Ni atoms, but might be caused by the ordering between the next nearest neighbor Cu and Al atoms. (author)

  11. The influence of the substrate on the adhesive strength of the micro-arc oxidation coating developed on TiNi shape memory alloy

    Science.gov (United States)

    Hsieh, Shy-Feng; Ou, Shih-Fu; Chou, Chia-Kai

    2017-01-01

    TiNi shape memory alloys (SMAs), used as long-term implant materials, have a disadvantage. Ni-ion release from the alloys may trigger allergies in the human body. Micro-arc oxidation has been utilized to modify the surface of the TiNi SMA for improving its corrosion resistance and biocompatibility. However, there are very few reports investigating the essential adhesive strength between the micro-arc oxidized film and TiNi SMA. Two primary goals were attained by this study. First, Ti50Ni48.5Mo1.5 SMA having a phase transformation temperature (Af) less than body temperature and good shape recovery were prepared. Next, the Ti50Ni50 and Ti50Ni48.5Mo1.5 SMA surfaces were modified by micro-arc oxidation in phosphoric acid by applying relatively low voltages to maintain the adhesive strength. The results indicated that the pore size, film thickness, and P content increased with applied voltage. The micro-arc oxidized film, comprising Ti oxides, Ni oxide, and phosphate compounds, exhibited a glassy amorphous structure. The outmost surface of the micro-arc oxidized film contained a large amount of P (>12 at%) but only a trace of Ni (micro-arc oxidized films exceeded the requirements of ISO 13779. Furthermore, Mo addition into TiNi SMAs was found to be favorable for improving the adhesive strength of the micro-arc oxidized film.

  12. Nitride coating enhances endothelialization on biomedical NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ion, Raluca [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Luculescu, Catalin [National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, P.O. Box MG-36, 077125 Magurele-Bucharest (Romania); Cimpean, Anisoara, E-mail: anisoara.cimpean@bio.unibuc.ro [University of Bucharest, Department of Biochemistry and Molecular Biology, 91-95 Spl. Independentei, 050095 Bucharest (Romania); Marx, Philippe [AMF Company, Route de Quincy, 18120 Lury-sur-Arnon (France); Gordin, Doina-Margareta; Gloriant, Thierry [INSA Rennes, UMR CNRS 6226 ISCR, 20 Avenue des Buttes de Coësmes, 35708 Rennes Cedex 7 (France)

    2016-05-01

    Surface nitriding was demonstrated to be an effective process for improving the biocompatibility of implantable devices. In this study, we investigated the benefits of nitriding the NiTi shape memory alloy for vascular stent applications. Results from cell experiments indicated that, compared to untreated NiTi, a superficial gas nitriding treatment enhanced the adhesion of human umbilical vein endothelial cells (HUVECs), cell spreading and proliferation. This investigation provides data to demonstrate the possibility of improving the rate of endothelialization on NiTi by means of nitride coating. - Highlights: • Gas nitriding process of NiTi is competent to promote cell spreading. • Surface nitriding of NiTi is able to stimulate focal adhesion formation and cell proliferation. • Similar expression pattern of vWf and eNOS was exhibited by bare and nitrided NiTi. • Gas nitriding treatment of NiTi shows promise for better in vivo endothelialization.

  13. Nonvolatile memory characteristics influenced by the different crystallization of Ni-Si and Ni-N nanocrystals

    International Nuclear Information System (INIS)

    Chen, W.-R.; Yeh, J.-L.; Chang, C.-Y.; Chang, T.-C.; Chen, S.-C.

    2008-01-01

    The formation of Ni-Si and Ni-N nanocrystals by sputtering a Ni 0.3 Si 0.7 target in argon and nitrogen environment were proposed in this paper. A transmission electron microscope analysis shows the nanocrystals embedded in the nitride layer. X-ray photoelectron spectroscopy and x-ray diffraction also offer the chemical material analysis of nanocrystals with surrounding dielectric and the crystallization of nanocrystals for different thermal annealing treatments. Nonvolatile Ni-Si nanocrystal memories reveal superior electrical characteristics for charge storage capacity and reliability due to the improvement of thermal annealing treatment. In addition, we used energy band diagrams to explain the significance of surrounding dielectric for reliability

  14. Fabrication of SLM NiTi Shape Memory Alloy via Repetitive Laser Scanning

    Science.gov (United States)

    Khoo, Zhong Xun; Liu, Yong; Low, Zhi Hong; An, Jia; Chua, Chee Kai; Leong, Kah Fai

    2018-01-01

    Additive manufacturing has the potential to overcome the poor machinability of NiTi shape-memory alloy in fabricating smart structures of complex geometry. In recent years, a number of research activities on selective laser melting (SLM) of NiTi have been carried out to explore the optimal parameters for producing SLM NiTi with the desired phase transformation characteristics and shape-memory properties. Different effects of energy density and processing parameters on the properties of SLM NiTi were reported. In this research, a new approach—repetitive laser scanning—is introduced to meet these objectives as well. The results suggested that the laser absorptivity and heat conductivity of materials before and after the first scan significantly influence the final properties of SLM NiTi. With carefully controlled repetitive scanning process, the fabricated samples have demonstrated shape-memory effect of as high as 5.11% (with an average value of 4.61%) and exhibited comparable transformation characteristics as the NiTi powder used. These results suggest the potential for fabricating complex NiTi structures with similar properties to that of the conventionally produced NiTi parts.

  15. Fabrication of SLM NiTi Shape Memory Alloy via Repetitive Laser Scanning

    Science.gov (United States)

    Khoo, Zhong Xun; Liu, Yong; Low, Zhi Hong; An, Jia; Chua, Chee Kai; Leong, Kah Fai

    2018-03-01

    Additive manufacturing has the potential to overcome the poor machinability of NiTi shape-memory alloy in fabricating smart structures of complex geometry. In recent years, a number of research activities on selective laser melting (SLM) of NiTi have been carried out to explore the optimal parameters for producing SLM NiTi with the desired phase transformation characteristics and shape-memory properties. Different effects of energy density and processing parameters on the properties of SLM NiTi were reported. In this research, a new approach—repetitive laser scanning—is introduced to meet these objectives as well. The results suggested that the laser absorptivity and heat conductivity of materials before and after the first scan significantly influence the final properties of SLM NiTi. With carefully controlled repetitive scanning process, the fabricated samples have demonstrated shape-memory effect of as high as 5.11% (with an average value of 4.61%) and exhibited comparable transformation characteristics as the NiTi powder used. These results suggest the potential for fabricating complex NiTi structures with similar properties to that of the conventionally produced NiTi parts.

  16. Magnetic and transport properties of EuNi(Si1-xGex)3 compounds

    International Nuclear Information System (INIS)

    Uchima, K; Takaesu, Y; Akamine, H; Kakihana, M; Tomori, K; Uejo, T; Teruya, A; Nakamura, A; Hedo, M; Nakama, T; Yagasaki, K; Matsubayashi, K; Uwatoko, Y

    2014-01-01

    The magnetization M, electrical resistivity ρ, thermopower S and specific heat C of EuNi(Si 1-x Ge x ) 3 compounds have been measured at temperatures from 2 to 300 K. For the compounds of EuNi(Si 1-x Ge x ) 3 , we obtained an effective magnetic moment of μ eff ∼ 7.7 μ B , which is close to the divalent Eu value of μ eff =7.94 μ B . All compounds of EuNi(Si 1-x Ge x ) 3 order antiferromagnetically. The Néel temperature T N decreases monotonously with increasing the Ge concentration x from T N =49 K for EuNiSi 3 to T N =14 K for EuNiGe 3 . In the low temperature region below T N , anomalies corresponding to an additional magnetic phase transition into ferromagnetic state for compounds with x < 0.3, and into another antiferromagnetic for x > 0.3 were observed. The Curie temperature T C rapidly decreases with increasing x and vanishes at x ≈ 0.3. It is found that the magnetic phase transition temperatures of T N and T C in EuNi(Si 1-x Ge x ) 3 are strongly connected with the change of volume induced by the atomic substitution of Si by Ge

  17. Effect of NiO growth conditions on the bipolar resistance memory switching of Pt/NiO/SRO structure

    International Nuclear Information System (INIS)

    Kurnia, F.; Hadiyawarman, H.; Jung, C. U.; Liu, C. L.; Lee, S. B.; Yang, S. M.; Park, H. W.; Song, S. J.; Hwang, C. S.

    2010-01-01

    We deposited NiO thin films with SrRuO 3 bottom electrodes on SrTiO 3 (001) substrates by using pulsed laser deposition. The growth temperature and the oxygen pressure were varied in order to obtain NiO films with different structural and electrical properties. We investigated the I-V characteristics of the Pt/NiO/SRO structures and observed a strong dependence of bipolar resistance switching on the growth conditions of the NiO thin films. Stable bipolar memory resistance switching was observed only in the devices with NiO films deposited at 400 .deg. C and 10 mTorr of O 2 . The off-state I-V curve of bipolar switching showed a linear fitting to the Schottky effect, indicating its origin in the NiO/SRO interface. Our results suggest that the growth conditions of NiO may affect the bipolar switching behavior through the film's resistance, the film's crystallinity, or the status of the grain boundaries.

  18. Surface microstructures and corrosion resistance of Ni-Ti-Nb shape memory thin films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Kun [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Faculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom); Li, Yan, E-mail: liyan@buaa.edu.cn [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Huang, Xu [Memry Corporation, Bethel, CT 06801 (United States); Gibson, Des [Institute of Thin Films, Sensors & Imaging, Scottish Universities Physics Alliance, University of the West of Scotland, Paisley PA1 2BE (United Kingdom); Zheng, Yang; Liu, Jiao; Sun, Lu [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Fu, Yong Qing, E-mail: richard.fu@northumbria.ac.uk [Faculty of Engineering and Environment, Northumbria University, Newcastle Upon Tyne NE1 8ST (United Kingdom)

    2017-08-31

    Highlights: • The corrosion resistance of Ni-Ti-Nb shape memory thin films is investigated. • Modified surface oxide layers improve the corrosion resistance of Ni-Ti-Nb films. • Further Nb additions reduce the potential corrosion tendency of the films. - Abstract: Ni-Ti-Nb and Ni-Ti shape memory thin films were sputter-deposited onto silicon substrates and annealed at 600 °C for crystallization. X-ray diffraction (XRD) measurements indicated that all of the annealed Ni-Ti-Nb films were composed of crystalline Ni-Ti (Nb) and Nb-rich grains. X-ray photoelectron spectroscopy (XPS) tests showed that the surfaces of Ni-Ti-Nb films were covered with Ti oxides, NiO and Nb{sub 2}O{sub 5}. The corrosion resistance of the Ni-Ti-Nb films in 3.5 wt.% NaCl solution was investigated using electrochemical tests such as open-circuit potential (OCP) and potentio-dynamic polarization tests. Ni-Ti-Nb films showed higher OCPs, higher corrosion potentials (E{sub corr}) and lower corrosion current densities (i{sub corr}) than the binary Ni-Ti film, which indicated a better corrosion resistance. The reason may be that Nb additions modified the passive layer on the film surface. The OCPs of Ni-Ti-Nb films increased with further Nb additions, whereas no apparent difference of E{sub corr} and i{sub corr} was found among the Ni-Ti-Nb films.

  19. PRECIPITATION HARDENING IN B2-ORDERED NiAl BY Ni2AlTiCOMPOUND

    Institute of Scientific and Technical Information of China (English)

    W.H. Tian; K. Ohishi; M. Nemoto

    2001-01-01

    Microstructural variations and correlated hardness changes in B2-ordered NiAl containing fine precipitation of Ni2AlTi have been investigated by means of transmission electron microscopy (TEM) and hardness tests. The amount of age hardening is not large as compared to the large microstructural variations during aging. TEM observations have revealed that the L21-type Ni2AlTi precipitates keep a lattice coherency with the NiAl matrix at the beginning of aging. By longer periods of aging Ni2AlTi precipitates lose their coherency and change their morphology to the globular ones surrounded by misfit dislocations. The temperature dependence of the yield strength of precipitate-containing B2-ordered NiAl was investigated by compression tests over the temperature range of 873-1273K. The fine precipitation of Ni2AlTi was found to enhance greatly the yield strength and the high-temperature strength is comparison with that of superalloy Mar-M200.``

  20. Surface microstructures and corrosion resistance of Ni-Ti-Nb shape memory thin films

    Science.gov (United States)

    Li, Kun; Li, Yan; Huang, Xu; Gibson, Des; Zheng, Yang; Liu, Jiao; Sun, Lu; Fu, Yong Qing

    2017-08-01

    Ni-Ti-Nb and Ni-Ti shape memory thin films were sputter-deposited onto silicon substrates and annealed at 600 °C for crystallization. X-ray diffraction (XRD) measurements indicated that all of the annealed Ni-Ti-Nb films were composed of crystalline Ni-Ti (Nb) and Nb-rich grains. X-ray photoelectron spectroscopy (XPS) tests showed that the surfaces of Ni-Ti-Nb films were covered with Ti oxides, NiO and Nb2O5. The corrosion resistance of the Ni-Ti-Nb films in 3.5 wt.% NaCl solution was investigated using electrochemical tests such as open-circuit potential (OCP) and potentio-dynamic polarization tests. Ni-Ti-Nb films showed higher OCPs, higher corrosion potentials (Ecorr) and lower corrosion current densities (icorr) than the binary Ni-Ti film, which indicated a better corrosion resistance. The reason may be that Nb additions modified the passive layer on the film surface. The OCPs of Ni-Ti-Nb films increased with further Nb additions, whereas no apparent difference of Ecorr and icorr was found among the Ni-Ti-Nb films.

  1. Moessbauer effect measurements on the intermetallic compounds Ni3Al and Ni3Ge

    International Nuclear Information System (INIS)

    Drijver, J.W.; Woude, F. van der

    1975-01-01

    Moessbauer parameters obtained from room temperature emission and absorption spectra of Ni 3 Al and Ni 3 Ga processed by a computer assuming a singlet and a doublet are given. The doublet is due to iron or cobalt atoms at the nickel site. Quadrupole splitting at 57 Fe nuclei in Ni 3 Ga is larger than in Ni 3 Al, viz. 0.52 and 0.37 mm/sec, respectively. Isomer shift at the Al/Ga position is very close to -0.02 mm/sec found in metallic nickel. Also given are the hyperfine magnetic fields at 4.2 K. Considering the preference of 57 Co and 57 Fe atoms in the lattice, the field intensities at the nickel and aluminium sites are found to be 227 +- 1 and 238 +- 1 kOe, respectively. (Z.S.)

  2. Microstructure, mechanical and functional properties of NiTi-based shape memory ribbons

    International Nuclear Information System (INIS)

    Mehrabi, K.; Bruncko, M.; Kneissl, A.C.

    2012-01-01

    Highlights: ► Melt-spun samples exhibited martensite structure and shape memory effects immediately after processing at room temperature. ► Using a new etchant and interference contrast, it is possible to reveal the fine microstructures and grain boundaries. ► The martensite structure in NiTi is very fine, and nano-sized twin boundaries could be revealed using TEM only. ► Two-way effects have been successfully introduced by different thermomechanical training methods in NiTi, NiTiCu and NiTiW alloys, which can be used for several applications, e.g. microsensors and microactuators. - Abstract: The present work has been aimed to study the microstructures, functional properties and the influence of different thermomechanical training methods on the two-way shape memory effect in NiTi-based melt-spun ribbons. In order to get small-dimensioned shape memory alloys (SMAs) with good functional and mechanical properties, a rapid solidification technique was employed. Their fracture and elasticity characteristics have been determined, as well as shape memory properties by thermomechanical cycling. The ribbons were trained under tensile and bending deformation by thermal cycling through the phase transformation temperature range. The results displayed that all different training methods were effective in developing a two-way shape memory effect (TWSME). The influence of copper (5–25 at.% Cu) and tungsten (2 at.% W) on the microstructure, and the functional and mechanical behavior of NiTi thin ribbons was also investigated. All samples show a shape memory effect immediately after processing without further heat treatment. The melt-spun ribbons were trained under constant strain (bending and tensile deformation) by thermal cycling through the phase transformation temperature range. The addition of copper was effective to narrow the transformation hysteresis. The W addition has improved the TWSME stability of the NiTi alloys and mechanical properties. Results about

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

    International Nuclear Information System (INIS)

    Gómez-Cortés, J.F.; San Juan, J.; López, G.A.; Nó, M.L.

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-10-01

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

  5. Thermal Expansion of Ni3Al Intermetallic Compound: Experiment and Simulation

    International Nuclear Information System (INIS)

    Wang Hai-Peng; Lü Peng; Zhou Kai; Wei Bing-Bo

    2016-01-01

    The thermal expansion of Ni 3 Al intermetallic compound is determined by a thermal dilatometer and simulated by the molecular dynamics method. The results of the linear thermal expansion coefficients are presented from 200 K up to the maximum temperature of 1600 K. The single phase of Ni 3 Al intermetallic compound is confirmed by x-ray diffraction together with DSC melting and solidification peaks, from which the solidus and the liquidus temperatures are obtained to be 1660 and 1695 K, respectively. The measured linear thermal expansion coefficient increases from 1.5 × 10 −5 to 2.7 × 10 −5 K −1 in the experimental temperature range, in good agreement with the data obtained by the molecular dynamics simulation, just a slight difference from the temperature dependence coefficient. Furthermore, the atomic structure and position are presented to reveal the atom distribution change during thermal expansion of Ni 3 Al compound. (paper)

  6. Local atomic and crystal structure rearrangement during the martensitic transformation in Ti50Ni25Cu25 shape memory alloy

    International Nuclear Information System (INIS)

    Menushenkov, Alexey; Grishina, Olga; Shelyakov, Alexander; Yaroslavtsev, Alexander; Zubavichus, Yan; Veligzhanin, Alexey; Bednarcik, Jozef; Chernikov, Roman; Sitnikov, Nikolay

    2014-01-01

    Highlights: • Local crystalline structure of TiNiCu SMA is investigated using EXAFS. • Peculiarities of Ni and Cu local environment are found. • Ti atoms show greater mobility relative to Ni atoms. • Ni local environment change is significant for shape memory effect. -- Abstract: The changes of crystal structure and local crystalline environment of Ti, Ni and Cu atoms in Ti 50 Ni 25 Cu 25 shape memory alloy are investigated using X-ray diffraction and extended X-ray absorption fine structure spectroscopy (EXAFS) in temperature range of martensite transformation. The analysis of the EXAFS-spectra shows that the bonds involving Ni atoms have the highest degree of disorder and the change in the local environment around Ni atoms is significant for the occurrence of the shape memory effect, while Cu atoms occupy the normal positions in the crystallographic structure and have the lowest displacement amplitude leading to the stabilization of both phases

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

    International Nuclear Information System (INIS)

    Kang, S.; Nam, T.

    2001-01-01

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

  8. Crystal structure of the Ce2Ni2Zn15 compound

    International Nuclear Information System (INIS)

    Opainich, I.M.; Pavlyuk, V.V.; Bodak, O.I.; Cherny, R.; Yvon, K.

    1996-01-01

    A structure of a new ternary compound of the composition Ce2Ni2Zn15 (sp.gr.R3-barm,a=0.9080(3) nm, c=1.3294(3) nm) was determined on single-crystal and powder specimens. The study was performed on a Philips PW1100 automatic diffractometer and a DRON-4.07 powder diffractometer. The Ce2Ni2Zn15 compound is crystallized in the Ce2Al2Co15 structure type with the aluminum positions being occupied by nickel and cobalt positions being occupied by zinc

  9. Powder metallurgy of NiTi-alloys with defined shape memory properties

    International Nuclear Information System (INIS)

    Bram, M.; Ahmad-Khanlou, A.; Buchkremer, H.P.; Stoever, D.

    2001-01-01

    The aim of the present work is the development of fabrication processes for NiTi shape memory alloys by powder metallurgical means. The starting materials used were prealloyed powders as well as elemental powder mixtures. Three techniques seem to be very promising for shaping of NiTi compacts. Hot Isostatic Pressing (HIP) has been examined for the production of dense semi-finished components. A promising technique for the production of dense and porous coatings with an increased wear resistance is Vacuum Plasma Spraying (VPS). Metal Injection Moulding (MIM) is especially suitable for near-net shape fabrication of small components with a complex geometry considering that large numbers of units have to be produced for compensating high tool and process costs. Subsequently, thermal treatments are required to establish defined shape memory properties. The reproducibility and stability of the shape memory effect are main aspects thinking about a production of NiTi components in an industrial scale. (author)

  10. Biocorrosion investigation of two shape memory nickel based alloys: Ni-Mn-Ga and thin film NiTi.

    Science.gov (United States)

    Stepan, L L; Levi, D S; Gans, E; Mohanchandra, K P; Ujihara, M; Carman, G P

    2007-09-01

    Thin film nitinol and single crystal Ni-Mn-Ga represent two new shape memory materials with potential to be used as percutaneously placed implant devices. However, the biocompatibility of these materials has not been adequately assessed. Immersion tests were conducted on both thin film nitinol and single crystal Ni-Mn-Ga in Hank's balanced salt solution at 37 degrees C and pH 7.4. After 12 h, large pits were found on the Ni-Mn-Ga samples while thin film nitinol displayed no signs of corrosion. Further electrochemical tests on thin film nitinol samples revealed breakdown potentials superior to a mechanically polished nitinol disc. These results suggest that passivation or electropolishing of thin film nitinol maybe unnecessary to promote corrosion resistance.

  11. 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.

  12. Magnetocaloric effect in textured rare earth intermetallic compound ErNi

    Directory of Open Access Journals (Sweden)

    Aparna Sankar

    2018-05-01

    Full Text Available Melt-spun ErNi crystallizes in orthorhombic FeB-type structure (Space group Pnma, no. 62 similar to the arc-melted ErNi compound. Room temperature X-ray diffraction (XRD experiments reveal the presence of texture and preferred crystal orientation in the melt-spun ErNi. The XRD data obtained from the free surface of the melt-spun ErNi show large intensity enhancement for (1 0 2 Bragg reflection. The scanning electron microscopy image of the free surface depicts a granular microstructure with grains of ∼1 μm size. The arc-melted and the melt-spun ErNi compounds order ferromagnetically at 11 K and 10 K (TC respectively. Field dependent magnetization (M-H at 2 K shows saturation behaviour and the saturation magnetization value is 7.2 μB/f.u. for the arc-melted ErNi and 7.4 μB/f.u. for the melt-spun ErNi. The isothermal magnetic entropy change (ΔSm close to TC has been calculated from the M-H data. The maximum isothermal magnetic entropy change, -ΔSmmax, is ∼27 Jkg-1K-1 and ∼24 Jkg-1K-1 for the arc-melted and melt-spun ErNi for 50 kOe field change, near TC. The corresponding relative cooling power values are ∼440 J/kg and ∼432 J/kg respectively. Although a part of ΔSm is lost to crystalline electric field (CEF effects, the magnetocaloric effect is substantially large at 10 K, thus rendering melt-spun ErNi to be useful in low temperature magnetic refrigeration applications such as helium gas liquefaction.

  13. Magnetocaloric effect in textured rare earth intermetallic compound ErNi

    Science.gov (United States)

    Sankar, Aparna; Chelvane, J. Arout; Morozkin, A. V.; Nigam, A. K.; Quezado, S.; Malik, S. K.; Nirmala, R.

    2018-05-01

    Melt-spun ErNi crystallizes in orthorhombic FeB-type structure (Space group Pnma, no. 62) similar to the arc-melted ErNi compound. Room temperature X-ray diffraction (XRD) experiments reveal the presence of texture and preferred crystal orientation in the melt-spun ErNi. The XRD data obtained from the free surface of the melt-spun ErNi show large intensity enhancement for (1 0 2) Bragg reflection. The scanning electron microscopy image of the free surface depicts a granular microstructure with grains of ˜1 μm size. The arc-melted and the melt-spun ErNi compounds order ferromagnetically at 11 K and 10 K (TC) respectively. Field dependent magnetization (M-H) at 2 K shows saturation behaviour and the saturation magnetization value is 7.2 μB/f.u. for the arc-melted ErNi and 7.4 μB/f.u. for the melt-spun ErNi. The isothermal magnetic entropy change (ΔSm) close to TC has been calculated from the M-H data. The maximum isothermal magnetic entropy change, -ΔSmmax, is ˜27 Jkg-1K-1 and ˜24 Jkg-1K-1 for the arc-melted and melt-spun ErNi for 50 kOe field change, near TC. The corresponding relative cooling power values are ˜440 J/kg and ˜432 J/kg respectively. Although a part of ΔSm is lost to crystalline electric field (CEF) effects, the magnetocaloric effect is substantially large at 10 K, thus rendering melt-spun ErNi to be useful in low temperature magnetic refrigeration applications such as helium gas liquefaction.

  14. Magnetic domain structure and domain-wall energy in UFe8Ni2Si2 and UFe6Ni4Si2 intermetallic compounds

    International Nuclear Information System (INIS)

    Wyslocki, J.J.; Suski, W.; Wochowski, K.

    1994-01-01

    Magnetic domain structures in the UFe 8 Ni 2 Si 2 and UFe 6 Ni 4 Si 2 compounds were studied using the powder pattern method. The domain structure observed is typical for uniaxial materials. The domain-wall energy density γ was determined from the average surface domain width D s observed on surfaces perpendicular to the easy axis as equal to 16 erg/cm 2 for UFe 8 Ni 2 Si 2 and 10 erg/cm 2 for UFe 6 Ni 4 Si 2 . Moreover, the critical diameter for single domain particle D c was calculated for the studied compounds

  15. RF magnetron sputtered TiNiCu shape memory alloy thin film

    International Nuclear Information System (INIS)

    Fu Yongqing; Du Hejun

    2003-01-01

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

  16. Shape memory effect and microstructures of sputter-deposited Cu-Al-Ni films

    International Nuclear Information System (INIS)

    Minemura, T.; Andoh, H.; Kita, Y.; Ikuta, I.

    1985-01-01

    The shape memory effect has been found in many alloy systems which exhibit a thermoelastic martensite transformation. Cu-Al-Ni alloys exhibit an excellent shape memory effect in single crystalline states, but they have not yet been commercially used due to their brittle fracture along the grain boundaries in polycrystalline states. This letter reports the shape memory effect and microstructures of the sputter-deposited Cu-Al-Ni films. Cu-14%Al-4%Ni alloy ingot was prepared. A target for sputter deposition was cut from the ingot. Aluminium foils (20 μm thick) were used for the substrates of sputter deposition. The microstructures and crystal structures of the films were investigated by transmission electron microscopy (TEM) and X-ray diffraction using CuKα radiation, respectively. The effect of the sputtering conditions such as substrate temperature, partial pressure of argon gas, and the sputtering power on the structures of sputter-deposited Cu-14%Al-4%Ni films were investigated by X-ray diffraction. Results are shown and discussed. Photographs demonstrate shape memory behaviour of Cu-14%Al-4%Ni films sputter-deposited on aluminium foils from (a) liquid nitrogen temperature to (d) room temperature. (author)

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

    Science.gov (United States)

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

    2018-03-01

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

  18. Pressure dependence of the Curie temperature in the Kondo lattice compound YbNiSn

    Energy Technology Data Exchange (ETDEWEB)

    Sparn, G; Thompson, J D [Los Alamos National Lab., NM (United States); Hamzic, A [Dept. of Physics, Zagreb (Yugoslavia)

    1992-04-03

    We have measured the magnetic susceptibility (2 K < T < 300 K) and the electrical resistivity under pressure (1.2 K < T < 300 K; p < 20 kbar) of the Kondo lattice compound YbNiSn, which may be considered as the ''hole'' analogue of the isostructural compound CeNiSn. In contrast with CeNiSn, YbNiSn does not show an energy gap at low temperatures but instead undergoes a magnetic phase transition at T{sub M} = 5.5 K. The magnetic state might be either a weakly ferromagnetic or a complex antiferromagnetic state. By applying pressure the room temperature resistance {rho}{sub RT} decreases, while T{sub M} increases. This behavior can be interpreted with respect to Doniach's Kondo necklace model as a decrease in the local exchange coupling constant J with increasing pressure, which reduces Kondo spin compensation and favors long-range magnetic order. These results show that the idea that YbNiSn is the hole counterpart to CeNiSn holds well for the properties such as dT{sub M}/dP and d{rho}{sub RT}/dP but that it fails in more detailed aspects, such as the origin of the energy gap formation. (orig.).

  19. Large magnetocaloric effect of GdNiAl{sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Dembele, S.N.; Ma, Z.; Shang, Y.F. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Fu, H., E-mail: fuhao@uestc.edu.cn [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Balfour, E.A. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Hadimani, R.L.; Jiles, D.C. [Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011 (United States); Ames Laboratory, US Department of Energy, Ames, IA 50011 (United States); Teng, B.H.; Luo, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2015-10-01

    This paper presents the structure, magnetic properties, and magnetocaloric effect of the polycrystalline compound GdNiAl{sub 2}. Powder X-ray diffraction (XRD) measurement and Rietveld refinement revealed that GdNiAl{sub 2} alloy is CuMgAl{sub 2}-type phase structure with about 1 wt% GdNi{sub 2}Al{sub 3} secondary phase. Magnetic measurements suggest that the compound is ferromagnetic and undergoes a second-order phase transition near 28 K. The maximum value of magnetic entropy change reaches 16.0 J/kg K for an applied magnetic field change of 0–50 kOe and the relative cooling power was 6.4×10{sup 2} J/kg. It is a promising candidate as a magnetocaloric material working near liquid hydrogen temperature (~20 K) exhibiting large relative cooling power. - Highlights: • Preferred orientation with axis of [010] was found in the GdNiAl{sub 2} compound. • The ΔS{sub Mmax} and the RCP are 16.0 J/kg K and 640 J/kg, respectively, for ΔH=50 kOe. • Relative low rare earth content in GdNiAl{sub 2} comparing with other candidates.

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

    OpenAIRE

    E. Łągiewka; Z. Lekston

    2007-01-01

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

  1. The pressure effect on magnetic properties of YNi5, LaNi5 i CeNi5 compounds

    International Nuclear Information System (INIS)

    Grechnev, G.E.; Logosha, A.V.; Panfilov, A.S.; Kuchin, A.G.; Vasil'ev, A.N.

    2012-01-01

    The pressure effect on electronic structure and magnetic properties of YNi 5 , LaNi 5 and CeNi 5 compounds is studied. For these systems high values of the magneto volume effect for magnetic susceptibility χ , d lnχ / d lnV ∼ 4-7, are obtained at low temperatures. The experimental data and ab initio calculated results of electronic structure and paramagnetic contributions to susceptibility indicate a close proximity of YNi 5 , LaNi 5 and CeNi 5 to the quantum critical point. It is found that in these exchange-enhanced itinerant paramagnets the orbital Van Vleck contribution to susceptibility amounts to 15-20% and should be taken into account for description of experimental χ and d ln V / d lnV values. The calculated spin and orbital paramagnetic moments, induced by an external magnetic field for atoms in the YNi 5 unit cell, demonstrate a nonuniform distribution of magnetization density and nontrivial competition between spin and orbital moments.

  2. Electronic structure, magnetic and transport properties of the Heusler shape memory alloy Mn{sub 2}NiGa

    Energy Technology Data Exchange (ETDEWEB)

    Blum, C.G.F. [Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, Mainz (Germany); Institute of Solid State Research, IFW Dresden, D-01171 Dresden (Germany); Ouardi, S.; Fecher, G.H.; Balke, B.; Felser, C. [Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, Mainz (Germany); Wurmehl, S.; Buechner, B. [Institute of Solid State Research, IFW Dresden, D-01171 Dresden (Germany); Ueda, S.; Kobayashi, K. [NIMS Beamline Station, National Institute for Materials Science, Hyogo 679-5148, Japan. (Germany)

    2011-07-01

    Magnetic shape memory based on Heusler compounds have received increasing interest, due their potential use for actuator and sensor applications. The single crystals Mn{sub 2}NiGa were grown by the optical floating zone method using a image furnace with vertical setup under a purified argon atmosphere. The both cubic (austenite) and tetragonal (martensite) phases of the sample were determined using temperature dependence powder x-ray diffraction XRD. The effect of martensitic transitions on the magnetic and transport properties of the compound was investigated by measuring the saturation magnetization, electrical resistivity {rho}(T), the Seebeck coefficient S(T) and magnetoresistance R{sub M}. All measurements detect clear signatures of the martensitic transition around room temperature with a thermal hysteresis up to 30 K. The electronic structures of the martensitic as well the austenitic phase were investigated using bulk-sensitive hard X-ray photoelectron spectroscopy (HAXPES).

  3. Martensitic transformation and shape memory effect in polycomponent TiNi-based alloys

    International Nuclear Information System (INIS)

    Khachin, V.N.; Voronin, V.P.; Sivokha, V.P.; Pushin, V.G.

    1995-01-01

    The results of martesitic transformation (MT) and shape memory effect (SME) in quaternary Ti 50 (NiCoCu) 50 , Ti 50 (NiFeCu) 50 and (TiAl) 50 (NiCu) 50 alloys studies are generalized in this paper. On alloying TiNi simultaneously by two elements, their individual effect on MT and SME is conserved. Martensitic transformations B2→R and B2→B19' are almost simultaneously realizing in a binary TiNi. One can selectively control each of two MT channels by selecting property of alloying elements. As a result, the alloys having any sequences of MT and their realizations temperatures, including simultaneous realization of two MTs at low temperatures, which was not observed earlier, can be produced. (orig.)

  4. 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.

  5. NI Based System for Seu Testing of Memory Chips for Avionics

    Directory of Open Access Journals (Sweden)

    Boruzdina Anna

    2016-01-01

    Full Text Available This paper presents the results of implementation of National Instrument based system for Single Event Upset testing of memory chips into neutron generator experimental facility, which used for SEU tests for avionics purposes. Basic SEU testing algorithm with error correction and constant errors detection is presented. The issues of radiation shielding of NI based system are discussed and solved. The examples of experimental results show the applicability of the presented system for SEU memory testing under neutrons influence.

  6. Sodium borohydride hydrolysis in the presence of intermetallic compound LaNi5

    International Nuclear Information System (INIS)

    Korobov, I.I.; Mozgina, N.G.

    1992-01-01

    Kinetics of catalytic hydrolysis of sodium borohydride in the 1 mol/l solution of caustic sodium within the range of 298-318 K in presence of LaNi 5 intermetallic compound is studied. It is established that the reaction has zero order by NaBH 4 and the first one by LaNi 5 . The apparent activation energy of NaBH 4 catalytic hydrolysis in presence of LaNi 5 , calculated on the basis of temperature dependence of reaction velocity, is constant within the temperature range under investigation and constitutes 56$+-$1.5 kJ/mol. Recombination of surface hydrogen on LaNi 5 in molecular one is limiting stage determining NaBH 4 hydrolysis rate

  7. Pitting Corrosion of Ni3(Si,Ti Intermetallic Compound at Various Chloride Concentrations

    Directory of Open Access Journals (Sweden)

    Gadang Priyotomo

    2013-10-01

    Full Text Available The pitting corrosion of Ni3(Si,Ti intermetallic compound was investigated as function of chloride concentration by using electrochemical method and scanning electron microscope in sodium chloride solutions at 293 K.  In addition, the pitting corrosion of type C276 alloy was also studied under the same experimental condition for comparison.  The pitting potential obtained for the intermetallic compound decreased with increasing chloride concentration.  The specific pitting potential and pitting potential of Ni3(Si,Ti were lower than those of C276 alloy, which means that the pitting corrosion resistance of C276 alloy was higher than that of Ni3(Si,Ti.

  8. Role of atomic bonding for compound and glass formation in Ni-Si, Pd-Si, and Ni-B systems

    Science.gov (United States)

    Tanaka, K.; Saito, T.; Suzuki, K.; Hasegawa, R.

    1985-11-01

    Valence electronic structures of crystalline compounds and glassy alloys of Ni silicides, Pd silicides, and Ni borides are studied by soft-x-ray spectroscopy over wide ranges of Si and B concentrations. The samples prepared include bulk compounds, glassy ribbons, and amorphous sputtered films. Silicon Kβ emissions of Ni and Pd silicides generally consist of a prominent peak fixed at ~=4.5 and ~=5.8 eV below the Fermi level EF, respectively, with a shoulder near EF which grows and shifts toward lower energy with increasing Si concentration. The former is identified as due to Si p-like states forming Si 3p-Ni 3d or Si 3p-Pd 4d bonding states while the latter as due to the corresponding antibonding states. Ni L3 and Pd L3 emissions of these silicides indicate that Ni 3d and Pd 4d states lie between the above two states. These local electronic configurations are consistent with partial-density-of-states (PDOS) calculations performed by Bisi and Calandra. Similar electronic configurations are suggested for Ni borides from B Kα and Ni L3 emissions. Differences of emission spectra between compounds and glasses of similar compositions are rather small, but some enhancement of the contribution of antibonding states to the PDOS near EF is suggested for certain glasses over that of the corresponding compounds. These features are discussed in connection with the compound stability and glass formability.

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

    Science.gov (United States)

    Ng, Ching Wei; Mahmud, Abdus Samad

    2017-12-01

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

  10. Shape memory and pseudoelastic properties of Fe-Mn-Si and Ti-Ni based alloys

    International Nuclear Information System (INIS)

    Guenin, G.

    1997-01-01

    The aim of this presentation is to analyse and discuss some recent advances in shape memory and pseudoelastic properties of different alloys. Experimental work in connection with theoretical ones will be reviewed. The first part is devoted to the microstructural origin of shape memory properties of Fe-Mn-Si based alloys (γ-ε transformation); the second part is a synthetic analysis of the effects of thermomechanical treatments on shape memory and pseudoelastic effects in Ti-Ni alloys, with some focus on the behaviour of the R phase introduced. (orig.)

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

    Czech Academy of Sciences Publication Activity Database

    Molnár, Peter; Van Humbeeck, J.

    2011-01-01

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

  12. Surface treatment of NiTi shape memory alloy by modified advanced oxidation process

    Institute of Scientific and Technical Information of China (English)

    CHU Cheng-lin; WANG Ru-meng; YIN Li-hong; PU Yue-pu; DONG Yin-sheng; GUO Chao; SHENG Xiao-bo; LIN Ping-hua; CHU Paul-K

    2009-01-01

    A modified advanced oxidation process(AOP) utilizing a UV/electrochemically-generated peroxide system was used to fabricate titania films on chemically polished NiTi shape memory alloy(SMA). The microstructure and biomedical properties of the film were characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), inductively-coupled plasma mass spectrometry(ICPMS), hemolysis analysis, and blood platelet adhesion test. It is found that the modified AOP has a high processing effectiveness and can result in the formation of a dense titania film with a Ni-free zone near its top surface. In comparison, Ni can still be detected on the outer NiTi surface by the conventional AOP using the UV/H2O2 system. The depth profiles of O, Ni, Ti show that the film possesses a smooth graded interface structure next to the NiTi substrate and this structure enhances the mechanical stability of titania film. The titania film can dramatically reduce toxic Ni ion release and also improve the hemolysis resistance and thromboresistance of biomedical NiTi SMA.

  13. Powder Metallurgy Fabrication of Porous 51(at.%)Ni-Ti Shape Memory Alloys for Biomedical Applications

    Science.gov (United States)

    Ibrahim, Mustafa K.; Hamzah, E.; Saud, Safaa N.; Nazim, E. M.

    2018-05-01

    The effect of time and temperature on the microwave sintering of 51(at.%)Ni-Ti shape memory alloys (SMAs) was investigated in the current research. Furthermore, the microstructure, mechanical properties, and bio-corrosion properties were analyzed based on the sintering conditions. The results revealed that the sintering condition of 700 °C for 15 min produced a part with coherent surface survey that does not exhibit gross defects. Increasing the sintering time and temperature created defects on the outer surface, while reducing the temperature to 550 °C severely affected the mechanical properties. The microstructure of these samples showed two regions of Ni-rich region and Ti-rich region between them Ti2Ni, NiTi, and Ni3Ti phases. The differential scanning calorimeter (DSC) curves of Ni-Ti samples exhibited a multi-step phase transformation B19'-R-B2 during heating and cooling. An increase in the sintering temperature from 550 to 700 °C was found to increase the fracture strength significantly and decreased the fracture strain slightly. Reducing the sintering temperature from 700 to 550 °C severely affected the corrosion behaviors of 51%Ni-Ti SMAs. This research aims to select the optimum parameters to produce Ni-Ti alloys with desired microstructure, mechanical properties, and corrosion behaviors for biomedical applications.

  14. Nanoscale compositional analysis of NiTi shape memory alloy films deposited by DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, S. K.; Mohan, S. [Centre for Nano Science and Engineering, Indian Institute of Science, Bangalore-560012 (India); Bysakh, S. [Central Glass and Ceramics Research Institute, Kolkata-700032 (India); Kumar, A.; Kamat, S. V. [Defence Metallurgical Research Laboratory, Hyderabad-500058 (India)

    2013-11-15

    The formation of surface oxide layer as well as compositional changes along the thickness for NiTi shape memory alloy thin films deposited by direct current magnetron sputtering at substrate temperature of 300 °C in the as-deposited condition as well as in the postannealed (at 600 °C) condition have been thoroughly studied by using secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, and scanning transmission electron microscopy-energy dispersive x-ray spectroscopy techniques. Formation of titanium oxide (predominantly titanium dioxide) layer was observed in both as-deposited and postannealed NiTi films, although the oxide layer was much thinner (8 nm) in as-deposited condition. The depletion of Ti and enrichment of Ni below the oxide layer in postannealed films also resulted in the formation of a graded microstructure consisting of titanium oxide, Ni{sub 3}Ti, and B2 NiTi. A uniform composition of B2 NiTi was obtained in the postannealed film only below a depth of 200–250 nm from the surface. Postannealed film also exhibited formation of a ternary silicide (Ni{sub x}Ti{sub y}Si) at the film–substrate interface, whereas no silicide was seen in the as-deposited film. The formation of silicide also caused a depletion of Ni in the film in a region ∼250–300 nm just above the film substrate interface.

  15. Reactive Stresses in Ni49Fe18Ga27Co6 Shape-Memory-Alloy Single Crystals

    Science.gov (United States)

    Averkin, A. I.; Krymov, V. M.; Guzilova, L. I.; Timashov, R. B.; Soldatov, A. V.; Nikolaev, V. I.

    2018-03-01

    The reactive stresses induced in Ni49Fe18Ga27Co6-alloy single crystals during martensitic transformations with a limited possibility of shape-memory-strain recovery have been experimentally studied. The data on these crystals are compared with the results obtained previously for Cu-Al-Ni, Ni-Ti, and Ni‒Fe-Ga crystals. The potential of application of the Ni49Fe18Ga27Co6 single crystals in designing drives and power motors is demonstrated.

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

    International Nuclear Information System (INIS)

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

    2008-01-01

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

  17. Ti Ni shape memory alloy film-actuated microstructures for a MEMS probe card

    Science.gov (United States)

    Namazu, Takahiro; Tashiro, Youichi; Inoue, Shozo

    2007-01-01

    This paper describes the development of a novel silicon (Si) cantilever beam device actuated by titanium-nickel (Ti-Ni) shape memory alloy (SMA) films. A Ti-Ni SMA film can yield high work output per unit volume, so a Ti-Ni film-actuated Si cantilever beam device is a prospective tool for use as a microelectromechanical system (MEMS) probe card that provides a relatively large contact force between the probe and electrode pad in spite of its minute size. Before fabrication of the device, the thermomechanical deformation behavior of Ti-Ni SMA films with various compositions was investigated in order to determine a sufficient constituent film for a MEMS actuator. As a result, Ti-Ni films having a Ti content of 50.2 to 52.6 atomic% (at%) were found to be usable for operation as a room temperature actuator. We have developed a Ti-Ni film-actuated Si cantilever beam device, which can produce a contact force by the cantilever bending when in contact, and also by the shape memory effect (SME) of the Ti-Ni film arising from Joule heating. The SME of the Ti-Ni film can generate an additional average contact force of 200 µN with application of 500 mW to the film. In addition to physical contact, a dependable electric contact between the Au film-coated probe tip and the Al film electrode was achieved. However, the contact resistance exhibited an average value of 25 Ω, which would have to be reduced for practical use. Reliability tests confirmed the durability of the Ti-Ni film-actuated Si cantilever-beam, in that the contact resistance was constant throughout a large number of physical contacts (>104 times).

  18. Synthesis and Thermoelectric Properties of Ni-Doped ZrCoSb Half-Heusler Compounds

    Directory of Open Access Journals (Sweden)

    Degang Zhao

    2018-01-01

    Full Text Available The Ni-doped ZrCo1−xNixSb half-Heusler compounds were prepared by arc-melting and spark plasma sintering technology. X-ray diffraction analysis results showed that all samples were crystallized in a half-Heusler phase. Thermoelectric properties of ZrCo1−xNixSb compounds were measured from room temperature to 850 K. The electrical conductivity and the absolute value of Seebeck coefficient increased with the Ni-doping content increasing due to the Ni substitution at Co. sites. The lattice thermal conductivity of ZrCo1−xNixSb samples was depressed dramatically because of the acoustic phonon scattering and point defect scattering. The figure of merit of ZrCo1−xNixSb compounds was improved due to the decreased thermal conductivity and improved power factor. The maximum ZT value of 0.24 was achieved for ZrCo0.92Ni0.08Sb sample at 850 K.

  19. Study on apatite compounds; Apataitokei kagobutsu ni kansuru kenkyu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-28

    To clarify the material properties of apatite compounds, the synthesis method, and the evaluation of physical properties of material and elementary technology were investigated. For the study on synthesis and crystal growth, a method of precipitating calcium phosphate on the surface of metal was investigated by means of relatively mild electrolytic method using liquid phase system. A new molding method of Ca defective apatite was established. Composite similar to vital bone was prepared by means of a new low-temperature sintering. For the study on chemical properties, from the model experiments, it was found that the self-organizing phenomenon, which is observed in the composite of apatite and collagen, happened between the organic single molecular film and crystal of apatite. For the study on evaluation of physical properties and elementary technology, the surface and interface of ceramics such as apatite were investigated by means of spectroscopy, the electronic state was analyzed by the quantum chemical calculation, and the crystalline structure was analyzed using X-ray equipment. 270 refs., 102 figs., 10 tabs.

  20. Work production using the two-way shape memory effect in NiTi and a Ni-rich NiTiHf high-temperature shape memory alloy

    International Nuclear Information System (INIS)

    Atli, K C; Karaman, I; Noebe, R D; Bigelow, G; Gaydosh, D

    2015-01-01

    The work output capacity of the two-way shape memory effect (TWSME) in a Ni 50.3 Ti 29.7 Hf 20 (at%) high-temperature shape memory alloy (HTSMA) was investigated and compared to that of binary Ni 49.9 Ti 50.1 (at%). TWSME was induced through a training procedure of 100 thermomechanical cycles under different tensile stresses. It was observed that TWSME in as-extruded and trained Ni 50.3 Ti 29.7 Hf 20 could produce 0.7% strain against a compressive stress of 100 MPa, corresponding to a maximum work output of 0.08 J g −1 , compared to a maximum value of 0.06 J g −1 for binary NiTi. A peak aging heat treatment of 3 h at 550 °C, which previously has been shown to result in near-perfect functional stability in Ni 50.3 Ti 29.7 Hf 20 during isobaric thermal cycling, did not improve the TWSME and actually resulted in a decrease in the magnitude and stability of the TWSME and its work output capacity. Nevertheless, the magnitude of TWSM behavior of Ni 50.3 Ti 29.7 Hf 20 , in the absence of an aging heat treatment, renders it an attractive candidate for high-temperature TWSM actuation. (paper)

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

    International Nuclear Information System (INIS)

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

    2002-01-01

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

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  3. Study of hyperfine interactions in intermetallic compounds Gd(Ni,Pd,Cu)In, Tb(Ni,Pd)In, Dy(Ni,Pd)In and Ho(Ni,Pd)In

    International Nuclear Information System (INIS)

    Lapolli, Andre Luis

    2006-01-01

    Systematic behavior of magnetic hyperfine field (B hf ) in the intermetallic compounds Gd(Ni,Pd,Cu)In Tb(Ni,Pd)In, Dy(Ni,Pd)In and Ho(Ni,Pd)In was studied by Perturbed Gamma-Gamma Angular Correlation spectroscopy. The measurements of B hf were carried out at the rare earth atom and in sites using the nuclear probes 140 Ce and 11 '1Cd respectively. The variation of hyperfine field with temperature, in most cases, follows the Brillouin function predicted from the molecular field theory. The hyperfine field values at rare earth atom sites obtained from 140 Ce probe as well as at in sites obtained from 111 Cd probe for each series of compounds were extrapolated to zero Kelvin B hf (T=0) from these curves. These values were compared with the values of the literature for other compounds containing the same rare earth element and all of them show a linear relationship with the ordering temperature. This indicates that the main contribution to B hf comes from the conduction electron polarization (CEP) through Fermi contact interaction and the principal mechanism of magnetic interaction in these compounds can be described by the RKKY type interaction. The values of B hf (T=0) for each family of intermetallic compounds RNiIn and RPdIn when plotted as a function of 4f spin projection of rare earth element also shows a linear relationship. Exceptions are the results for the compounds RNiIn obtained with 111 Cd probe where a small deviation from linearity is observed. The results of the measurements carried out with the 111 Cd probe were also analyzed to obtain the hyperfine parameters of the quadrupole interaction as a function of temperature for RPdln and GdNiIn compounds. The results show that for the compound GdPdIn there might be some Gd-In disorder at high temperature. (author)

  4. First-principles calculations of two cubic fluoropervskite compounds: RbFeF3 and RbNiF3

    International Nuclear Information System (INIS)

    Mubarak, A.A.; Al-Omari, Saleh

    2015-01-01

    We present first-principles calculations of the structural, elastic, electronic, magnetic and optical properties for RbFeF 3 and RbNiF 3 . The full-potential linear augmented plan wave (FP-LAPW) method within the density functional theory was utilized to perform the present calculations. We employed the generalized gradient approximation as exchange-correlation potential. It was found that the calculated analytical lattice parameters agree with previous studies. The analysis of elastic constants showed that the present compounds are elastically stable and anisotropic. Moreover, both compounds are classified as a ductile compound. The calculations of the band structure and density functional theory revealed that the RbFeF 3 compound has a half-metallic behavior while the RbNiF 3 compound has a semiconductor behavior with indirect (M–Γ) band gap. The ferromagnetic behavior was studied for both compounds. The optical properties were calculated for the radiation of up to 40 eV. A beneficial optics technology is predicted as revealed from the optical spectra. - Highlights: • RbFeF 3 and RbNiCl 3 compounds are elastically stable. • RbFeF 3 and RbNiCl 3 compounds are classified as a ductile compound. • The RbFeF 3 compound has a half-metallic behavior while the RbNiF 3 compound has a semiconductor behavior. • The optical properties were calculated for the radiation of up to 40 eV

  5. Experimental study on Response Parameters of Ni-rich NiTi Shape Memory Alloy during Wire Electric Discharge Machining

    Science.gov (United States)

    Bisaria, Himanshu; Shandilya, Pragya

    2018-03-01

    Nowadays NiTi SMAs are gaining more prominence due to their unique properties such as superelasticity, shape memory effect, high fatigue strength and many other enriched physical and mechanical properties. The current studies explore the effect of machining parameters namely, peak current (Ip), pulse off time (TOFF), and pulse on time (TON) on wire wear ratio (WWR), and dimensional deviation (DD) in WEDM. It was found that high discharge energy was mainly ascribed to high WWR and DD. The WWR and DD increased with the increase in pulse on time and peak current whereas high pulse off time was favourable for low WWR and DD.

  6. Laser welding of NiTi shape memory alloy: Comparison of the similar and dissimilar joints to AISI 304 stainless steel

    Science.gov (United States)

    Mirshekari, G. R.; Saatchi, A.; Kermanpur, A.; Sadrnezhaad, S. K.

    2013-12-01

    The unique properties of NiTi alloy, such as its shape memory effect, super-elasticity and biocompatibility, make it ideal material for various applications such as aerospace, micro-electronics and medical device. In order to meet the requirement of increasing applications, great attention has been given to joining of this material to itself and to other materials during past few years. Laser welding has been known as a suitable joining technique for NiTi shape memory alloy. Hence, in this work, a comparative study on laser welding of NiTi wire to itself and to AISI 304 austenitic stainless steel wire has been made. Microstructures, mechanical properties and fracture morphologies of the laser joints were investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), Vickers microhardness (HV0.2) and tensile testing techniques. The results showed that the NiTi-NiTi laser joint reached about 63% of the ultimate tensile strength of the as-received NiTi wire (i.e. 835 MPa) with rupture strain of about 16%. This joint also enabled the possibility to benefit from the pseudo-elastic properties of the NiTi component. However, tensile strength and ductility decreased significantly after dissimilar laser welding of NiTi to stainless steel due to the formation of brittle intermetallic compounds in the weld zone during laser welding. Therefore, a suitable modification process is required for improvement of the joint properties of the dissimilar welded wires.

  7. Superconducting properties of Zr1+xNi2-xGa and Zr1-xNi2+xGa Heusler compounds

    Directory of Open Access Journals (Sweden)

    Saad Alzahrani

    2017-05-01

    Full Text Available The superconducting properties of a series of Zr1+xNi2-xGa and Zr1-xNi2+xGa compounds have been investigated by x-ray diffraction, electrical resistivity, dc magnetization, and ac susceptibility measurements. While the parent compound, ZrNi2Ga, exhibited the cubic L21 Heusler structure, multiple non-cubic structures formed in the Zr and Ni rich doped materials. For x ≤ 0.3, all Zr1-xNi2+xGa compounds demonstrated superconducting behavior, but no superconductivity was observed in the Zr1+xNi2-xGa alloys for x > 0.2. The magnetization data revealed that all materials in both Zr1+xNi2-xGa and Zr1-xNi2+xGa series exhibited type-II superconductivity. With increasing doping concentration x, the paramagnetic ordering were enhanced in both systems while the superconducting properties were found to weaken. The observations are discussed considering the structural disorders in the systems.

  8. Reaction pathways of model compounds of biomass-derived oxygenates on Fe/Ni bimetallic surfaces

    Science.gov (United States)

    Yu, Weiting; Chen, Jingguang G.

    2015-10-01

    Controlling the activity and selectivity of converting biomass-derivatives to fuels and valuable chemicals is critical for the utilization of biomass feedstocks. There are primarily three classes of non-food competing biomass, cellulose, hemicellulose and lignin. In the current work, glycolaldehyde, furfural and acetaldehyde are studied as model compounds of the three classes of biomass-derivatives. Monometallic Ni(111) and monolayer (ML) Fe/Ni(111) bimetallic surfaces are studied for the reaction pathways of the three biomass surrogates. The ML Fe/Ni(111) surface is identified as an efficient surface for the conversion of biomass-derivatives from the combined results of density functional theory (DFT) calculations and temperature programmed desorption (TPD) experiments. A correlation is also established between the optimized adsorption geometry and experimental reaction pathways. These results should provide helpful insights in catalyst design for the upgrading and conversion of biomass.

  9. On the development of high quality NiTi shape memory and pseudoelastic parts by additive manufacturing

    International Nuclear Information System (INIS)

    Haberland, Christoph; Elahinia, Mohammad; Walker, Jason M; Meier, Horst; Frenzel, Jan

    2014-01-01

    Additive manufacturing provides an attractive processing method for nickel–titanium (NiTi) shape memory and pseudoelastic parts. In this paper, we show how the additive manufacturing process affects structural and functional properties of additively manufactured NiTi and how the process parameter set-up can be optimized to produce high quality NiTi parts and components. Comparisons of shape recovery due to shape memory and pseudoelasticity in additively manufactured and commercial NiTi exhibit promising potential for this innovative processing method. (paper)

  10. Steam reforming of different biomass tar model compounds over Ni/Al_2O_3 catalysts

    International Nuclear Information System (INIS)

    Artetxe, Maite; Alvarez, Jon; Nahil, Mohamad A.; Olazar, Martin; Williams, Paul T.

    2017-01-01

    Highlights: • Order of reactivity: anisole > furfural > indene > phenol > toluene > methyl naphthalene. • Higher coke deposition for oxygenates (1.5–2.8%) than for aromatics (0.5–0.8%). • Amorphous coke is deposited for oxygenates and filamentous carbon for aromatics. • Ni content of 20 wt.% shows the higher conversion (90%) and H_2 potential (63%). - Abstract: This work focuses on the removal of the tar derived from biomass gasification by catalytic steam reforming on Ni/Al_2O_3 catalysts. Different tar model compounds (phenol, toluene, methyl naphthalene, indene, anisole and furfural) were individually steam reformed (after dissolving each one in methanol), as well as a mixture of all of them, at 700 °C under a steam/carbon (S/C) ratio of 3 and 60 min on stream. The highest conversions and H_2 potential were attained for anisole and furfural, while methyl naphthalene presented the lowest reactivity. Nevertheless, the higher reactivity of oxygenates compared to aromatic hydrocarbons promoted carbon deposition on the catalyst (in the 1.5–2.8 wt.% range). When the concentration of methanol is decreased in the feedstock and that of toluene or anisole is increased, the selectivity to CO is favoured in the gaseous products, thus increasing coke deposition on the catalyst and decreasing catalyst activity for the steam reforming reaction. Moreover, an increase in Ni loading in the catalyst from 5 to 20% enhances carbon conversion and H_2 formation in the steam reforming of a mixture of all the model compounds studied, but these values decrease for a Ni content of 40%. Coke formation also increased by increasing Ni loading, attaining its maximum value for 40% Ni (6.5 wt.%).

  11. Neutron diffraction determination of atomic mean-square displacements in cubic compounds of Ni-Al and Ni-Al-Cu systems

    International Nuclear Information System (INIS)

    Khidirov, I.; Mukhtarova, N.N.

    2002-01-01

    The atomic mean-square displacements (AMSD) are some of important characteristics of the solid and can be the main information for determination of a number of other characteristics of substances. In the work AMSD is determined for a number of cubic compounds of Ni-Al, Ni-Al-Cu systems immediately from intensities of neutron diffraction maxima. It is shown by the offered method that in all NiAl x and NiAlCu x compounds with the CsCl - type structure AMSD are near each other and they are practically constant. Therefore it is possible to assume that within the homogeneity region of these compounds the interatomic bond forces are changed insignificantly

  12. Determination of the enthalpy of formation of Ni-Al intermetallic compounds using differential scanning calorimetry technique

    International Nuclear Information System (INIS)

    Kubaski, Evaldo Toniolo; Capocchi, Jose Deodoro Trani; Cintho, Osvaldo Mitsuyuki

    2010-01-01

    The compositions Ni20Al80, Ni25Al75, Ni40Al60, Ni50Al50, Ni60Al40 and Ni75Al25 (at. %) were heated in a calibrated thermal analysis equipment. All runs were conducted at a heating rate of 10 deg C/min under a dynamic argon atmosphere. Each composition was heated until the completion of the corresponding exothermic reaction responsible for intermetallic compound formation, and, also heated to 1480 deg C. The products obtained were characterized using X ray diffraction in order to identify the intermetallic compounds that were synthesized. Moreover, the results were evaluated using variance analysis. As a result, enthalpies of formation of Ni 2 Al 3 and Ni 3 Al compounds were determined by means of this methodology. Experimental values were 167 kJ/mol and 93 kJ/mol for Ni 2 Al 3 and Ni 3 Al, respectively. The former is 18% lower than the value found on literature, while the latter is 6% greater. (author)

  13. 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.

  14. Mechanochemical Synthesis of Nanostructured MgXNi1-XO Compound by Mg-NiO Mixture

    Directory of Open Access Journals (Sweden)

    Nader Setoudeh

    2017-06-01

    Full Text Available Synthesis of magnesium nickel oxide phase such as MgxNi1-xO solid solutions has been studied in this research article using mechnochmical reaction between magnesium and nickel oxide. Mixtures of magnesium powder and nickel oxide (Mg+NiO with stoichiometric compositions were milled for different times in a planetary ball mill. Reduction reaction of nickel oxide by magnesium via a mechanically induced self-sustaining reaction (MSR was confirmed in the XRD measurements of the as-milled samples. Formation of nanostructured magnesium nickel oxide phases (such as Mg0.4Ni0.6O or MgNiO2 was observed after isothermal heating of the 30 minutes milled samples at 1000°C where nickel phase seems to disappear in XRD patterns. The traces of phases such as Mg0.4Ni0.6O or MgNiO2 were also observed in the as-milled mixtures. Therefore, the XRD results of the as-milled samples suggested that the formation of magnesium nickel oxide phases could be possible even after prolonged milling. The XRD and SEM results of both as-milled and isothermally heated samples indicated that the crystallite size and particle size of the final products reached to nanoscale after milling. Morphological and compositional evolution of the samples after heat treatment was monitored through SEM imaging and elemental analyses. The results confirmed that the composition of final product is close to Mg0.4Ni0.6O compound.

  15. Fast Response Shape Memory Effect Titanium Nickel (TiNi) Foam Torque Tubes

    Science.gov (United States)

    Jardine, Peter

    2014-01-01

    Shape Change Technologies has developed a process to manufacture net-shaped TiNi foam torque tubes that demonstrate the shape memory effect. The torque tubes dramatically reduce response time by a factor of 10. This Phase II project matured the actuator technology by rigorously characterizing the process to optimize the quality of the TiNi and developing a set of metrics to provide ISO 9002 quality assurance. A laboratory virtual instrument engineering workbench (LabVIEW'TM')-based, real-time control of the torsional actuators was developed. These actuators were developed with The Boeing Company for aerospace applications.

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

    International Nuclear Information System (INIS)

    Ju, X; Dong, H

    2007-01-01

    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

  17. 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.

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

    International Nuclear Information System (INIS)

    Inagaki, Hirosuke

    1992-01-01

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

  19. Thermal and electron transport studies on the valence fluctuating compound YbNiAl4

    Science.gov (United States)

    Falkowski, M.; Kowalczyk, A.

    2018-05-01

    We report the thermoelectric power S and thermal conductivity κ measurements on the valence fluctuating compound YbNiAl4, furthermore taking into account the impact of the applied magnetic field. We discuss our new results with revisiting the magnetic [χ(T)], transport [ρ(T)], and thermodynamic [Cp(T)] properties in order to better understand the phenomenon of thermal and electron transport in this compound. The field dependence of the magnetoresistivity data is also given. The temperature dependence of thermoelectric power S(T) was found to exhibit a similar behaviour as expected for Yb-based compounds with divalent or nearly divalent Yb ions. In addition, the values of total thermal conductivity as a function of temperature κ(T) of YbNiAl4 are fairly low compared to those of pure metals which may be linked to the fact that the conduction band is perturbed by strong hybridization. A deeper analysis of the specific heat revealed the low-T anomaly of the ratio Cp(T)/T3, most likely associated with the localized low-frequency oscillators in this alloy. In addition, the Kadowaki-Woods ratio and the Wilson ratio are discussed with respect to the electronic correlations in YbNiAl4.

  20. Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

    Science.gov (United States)

    Benafan, Othmane

    2012-01-01

    The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

  1. Homogeneous (Cu, Ni)6Sn5 intermetallic compound joints rapidly formed in asymmetrical Ni/Sn/Cu system using ultrasound-induced transient liquid phase soldering process.

    Science.gov (United States)

    Li, Z L; Dong, H J; Song, X G; Zhao, H Y; Tian, H; Liu, J H; Feng, J C; Yan, J C

    2018-04-01

    Homogeneous (Cu, Ni) 6 Sn 5 intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni) 6 Sn 5 and minor Cu 3 Sn IMCs, and the grain morphology of (Cu, Ni) 6 Sn 5 IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni) 6 Sn 5 IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa). Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Atomistic characterization of pseudoelasticity and shape memory in NiTi nanopillars

    International Nuclear Information System (INIS)

    Zhong Yuan; Gall, Ken; Zhu Ting

    2012-01-01

    Molecular dynamics simulations are performed to study the atomistic mechanisms governing the pseudoelasticity and shape memory in nickel–titanium (NiTi) nanostructures. For a 〈1 1 0〉 – oriented nanopillar subjected to compressive loading–unloading, we observe either a pseudoelastic or shape memory response, depending on the applied strain and temperature that control the reversibility of phase transformation and deformation twinning. We show that irreversible twinning arises owing to the dislocation pinning of twin boundaries, while hierarchically twinned microstructures facilitate the reversible twinning. The nanoscale size effects are manifested as the load serration, stress plateau and large hysteresis loop in stress–strain curves that result from the high stresses required to drive the nucleation-controlled phase transformation and deformation twinning in nanosized volumes. Our results underscore the importance of atomistically resolved modeling for understanding the phase and deformation reversibilities that dictate the pseudoelasticity and shape memory behavior in nanostructured shape memory alloys.

  3. Study of hyperfine interactions in intermetallic compounds Gd(Ni,Pd,Cu)In, Tb(Ni,Pd)In, Dy(Ni,Pd)In and Ho(Ni,Pd)In; Estudo de interacoes hiperfinas em compostos intermetalicos Gd(Ni,Pd,Cu)In, Tb(Ni,Pd)In, Dy(Ni,Pd)In e Ho(Ni,Pd)In

    Energy Technology Data Exchange (ETDEWEB)

    Lapolli, Andre Luis

    2006-07-01

    Systematic behavior of magnetic hyperfine field (B{sub hf}) in the intermetallic compounds Gd(Ni,Pd,Cu)In Tb(Ni,Pd)In, Dy(Ni,Pd)In and Ho(Ni,Pd)In was studied by Perturbed Gamma-Gamma Angular Correlation spectroscopy. The measurements of B{sub hf} were carried out at the rare earth atom and in sites using the nuclear probes {sup 140}Ce and {sup 11}'1Cd respectively. The variation of hyperfine field with temperature, in most cases, follows the Brillouin function predicted from the molecular field theory. The hyperfine field values at rare earth atom sites obtained from {sup 140}Ce probe as well as at in sites obtained from {sup 111}Cd probe for each series of compounds were extrapolated to zero Kelvin B{sub hf}(T=0) from these curves. These values were compared with the values of the literature for other compounds containing the same rare earth element and all of them show a linear relationship with the ordering temperature. This indicates that the main contribution to B{sub hf} comes from the conduction electron polarization (CEP) through Fermi contact interaction and the principal mechanism of magnetic interaction in these compounds can be described by the RKKY type interaction. The values of B{sub hf}(T=0) for each family of intermetallic compounds RNiIn and RPdIn when plotted as a function of 4f spin projection of rare earth element also shows a linear relationship. Exceptions are the results for the compounds RNiIn obtained with {sup 111}Cd probe where a small deviation from linearity is observed. The results of the measurements carried out with the {sup 111}Cd probe were also analyzed to obtain the hyperfine parameters of the quadrupole interaction as a function of temperature for RPdln and GdNiIn compounds. The results show that for the compound GdPdIn there might be some Gd-In disorder at high temperature. (author)

  4. Study of hyperfine interactions in intermetallic compounds Gd(Ni,Pd,Cu)In, Tb(Ni,Pd)In, Dy(Ni,Pd)In and Ho(Ni,Pd)In; Estudo de interacoes hiperfinas em compostos intermetalicos Gd(Ni,Pd,Cu)In, Tb(Ni,Pd)In, Dy(Ni,Pd)In e Ho(Ni,Pd)In

    Energy Technology Data Exchange (ETDEWEB)

    Lapolli, Andre Luis

    2006-07-01

    Systematic behavior of magnetic hyperfine field (B{sub hf}) in the intermetallic compounds Gd(Ni,Pd,Cu)In Tb(Ni,Pd)In, Dy(Ni,Pd)In and Ho(Ni,Pd)In was studied by Perturbed Gamma-Gamma Angular Correlation spectroscopy. The measurements of B{sub hf} were carried out at the rare earth atom and in sites using the nuclear probes {sup 140}Ce and {sup 11}'1Cd respectively. The variation of hyperfine field with temperature, in most cases, follows the Brillouin function predicted from the molecular field theory. The hyperfine field values at rare earth atom sites obtained from {sup 140}Ce probe as well as at in sites obtained from {sup 111}Cd probe for each series of compounds were extrapolated to zero Kelvin B{sub hf}(T=0) from these curves. These values were compared with the values of the literature for other compounds containing the same rare earth element and all of them show a linear relationship with the ordering temperature. This indicates that the main contribution to B{sub hf} comes from the conduction electron polarization (CEP) through Fermi contact interaction and the principal mechanism of magnetic interaction in these compounds can be described by the RKKY type interaction. The values of B{sub hf}(T=0) for each family of intermetallic compounds RNiIn and RPdIn when plotted as a function of 4f spin projection of rare earth element also shows a linear relationship. Exceptions are the results for the compounds RNiIn obtained with {sup 111}Cd probe where a small deviation from linearity is observed. The results of the measurements carried out with the {sup 111}Cd probe were also analyzed to obtain the hyperfine parameters of the quadrupole interaction as a function of temperature for RPdln and GdNiIn compounds. The results show that for the compound GdPdIn there might be some Gd-In disorder at high temperature. (author)

  5. Precipitation Strengthenable NiTiPd High Temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen; Garg, Anita; Benafan, Othmane; Noebe, Ronald; Gaydosh, Darrell; Padula, Santo, II

    2017-01-01

    In binary NiTi alloys, it has long been known that Ni-rich alloys can be heat treated to produce precipitates which both strengthen the matrix against dislocations and improve the behavior of the material under thermal and mechanical cycling. Within recent years, the same effect has been observed in Ni-rich NiTiHf high temperature shape memory alloys and heat treatment regimens have been defined which will reliably produce improved properties. In NiTiPd alloys, precipitation has also been observed, but studies are still underway to define reliable heat treatments and compositions which will provide a balance of strengthening and good thermomechanical properties. For this study, a series of NiTi-32 at.Pd alloys was produced to determine the effect of changing nickeltitanium content on the transformation behavior and heat treatability of the material. Samples were aged at temperatures between 350C and 450C for times up to 100 hours. Actuation type behavior was evaluated using uniaxial constant force thermal cycling (UCFTC) to determine the effect of composition and aging on the material behavior. TEMSEM was used to evaluate the microstructure and determine the types of precipitates formed. The correlation between composition, heat treat, microstructure, and thermomechanical behavior will be addressed and discussed.

  6. Influence of cold working on deformation behavior and shape memory effect of Ti-Ni-Nb

    International Nuclear Information System (INIS)

    Okita, K.; Semba, H.; Okabe, N.; Sakuma, T.; Mihara, Y.

    2005-01-01

    In this study, the influence of cold working on the deformation behavior and the transformation characteristics was investigated on the Ti-Ni-Nb shape memory alloy (SMA). Both the tensile test and the shape recovery test were performed for the wire specimens of 1mm in the diameter with some different rates of cold working. The shape recovery tests were performed for the wire specimens of different cold working rates until the various levels of maximum applied strain, and the reverse-transformation characteristics on the process of heating after unloading were studied. It is clarified that the higher cold-working rate improves the shape memory properties of the alloy. (orig.)

  7. The ferromagnetic shape-memory effect in Ni-Mn-Ga

    International Nuclear Information System (INIS)

    Marioni, M.A.; O'Handley, R.C.; Allen, S.M.; Hall, S.R.; Paul, D.I.; Richard, M.L.; Feuchtwanger, J.; Peterson, B.W.; Chambers, J.M.; Techapiesancharoenkij, R.

    2005-01-01

    Active materials have long been used in the construction of sensors and devices. Examples are piezo-electric ceramics and shape memory alloys. The more recently developed ferromagnetic shape-memory alloys (FSMAs) have received considerable attention due to their large magnetic field-induced, reversible strains (up to 10%). In this article, we review the basic physical characteristics of the FSMA Ni-Mn-Ga (crystallography, thermal, mechanical and magnetic behavior). Also, we present some of the works currently under way in the areas of pulse-field and acoustic-assisted actuation, and vibration energy absorption

  8. CuNi Nanoparticles Assembled on Graphene for Catalytic Methanolysis of Ammonia Borane and Hydrogenation of Nitro/Nitrile Compounds

    International Nuclear Information System (INIS)

    Yu, Chao

    2017-01-01

    Here we report a solution phase synthesis of 16 nm CuNi nanoparticles (NPs) with the Cu/Ni composition control. These NPs are assembled on graphene (G) and show Cu/Ni composition-dependent catalysis for methanolysis of ammonia borane (AB) and hydrogenation of aromatic nitro (nitrile) compounds to primary amines in methanol at room temperature. Among five different CuNi NPs studied, the G-Cu 36 Ni 64 NPs are the best catalyst for both AB methanolysis (TOF = 49.1 mol H2 mol CuNi -1 min -1 and E a = 24.4 kJ/mol) and hydrogenation reactions (conversion yield >97%). In conclusion, the G-CuNi represents a unique noble-metal-free catalyst for hydrogenation reactions in a green environment without using pure hydrogen.

  9. Fracture behaviour of Cu-Al-Ni shape memory alloys obtained by powder metallurgy

    International Nuclear Information System (INIS)

    Rodriguez, P. P.; Perez-Saez, R. B.; Recarte, V.; San Juan, J.M.; Ruano, O. A.; No, M. L.

    2001-01-01

    Polycrystalline Cu-Al-Ni shape memory alloys have been scarcely employed for technological applications due to their high brittleness. The development of a new elaboration technique based on powder metallurgy has recently overcome this problem, through the improvement of the ductility of the produced alloys without affecting its shape memory properties. The fracture behaviour of an alloy obtained using the elaboration technique has been studied by means of Scanning Electron Microscopy and mechanical testing. The results show a ductile fracture with a maximum strain close to 13%, which is the best fracture behaviour obtained for Cu-Al-Ni polycrystals. The microstructure of such alloys ha been studied by means of Transmission Electron Microscopy, showing a poligonyzed structure in which martensite plated passing through the subboundaries easily. (Author) 19 refs

  10. 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).

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

    Science.gov (United States)

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

    2018-03-01

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

  12. Magnetic and calorimetric investigations of ferromagnetic shape memory alloy Ni54Fe19Ga27

    International Nuclear Information System (INIS)

    Sharma, V K; Chattopadhyay, M K; Kumar, Ravi; Ganguli, Tapas; Kaul, Rakesh; Majumdar, S; Roy, S B

    2007-01-01

    We report results of magnetization and differential scanning calorimetry measurements in the ferromagnetic shape memory alloy Ni 54 Fe 19 Ga 27 . This alloy undergoes an austenite-martensite phase transition in its ferromagnetic state. The nature of the ferromagnetic state, both in the austenite and the martensite phase, is studied in detail. The ferromagnetic state in the martensite phase is found to have higher anisotropy energy as compared with the austenite phase. The estimated anisotropy constant is comparable to that of a well-studied ferromagnetic shape memory alloy system NiMnGa. Further, the present study highlights various interesting features accompanying the martensitic transition (MT). These features suggest the possibility of either a premartensitic transition and/or an inter-MT in this system

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

    Czech Academy of Sciences Publication Activity Database

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

    2001-01-01

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

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

    Science.gov (United States)

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

    2018-03-01

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

  15. Experimental investigation on local mechanical response of superelastic NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Xiao, Yao; Zeng, Pan; Lei, Liping

    2016-01-01

    In this paper, primary attention is paid to the local mechanical response of NiTi shape memory alloy (SMA) under uniaxial tension. With the help of in situ digital image correlation, sets of experiments are conducted to measure the local strain field at various thermomechanical conditions. Two types of mechanical responses of NiTi SMA are identified. The residual strain localization phenomena are observed, which can be attributed to the localized phase transformation (PT) and we affirm that most of the irreversibility is accumulated simultaneously during PT. It is found that temperature and PT play important roles in inducing delocalization of the reverse transformation. We conclude that forward transformation has more influence on the transition of mechanical response in NiTi SMA than reverse transformation in terms of the critical transition temperature for inducing delocalized reverse transformation. (technical note)

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

    International Nuclear Information System (INIS)

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

    1999-01-01

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

  17. Fabrication and AE characteristics of TiNi/A16061 shape memory alloy composite

    International Nuclear Information System (INIS)

    Park, Young Chul; Lee, Jin Kyung

    2004-01-01

    TiNi/A16061 Shape Memory Alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which underwent pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/A16061 SMA composite

  18. Laser beam welding of NiTi-shape memory alloys; Laserstrahl-Schweissen von NiTi-Formgedaechtnislegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Haas, T.

    1996-04-01

    Using a Nd:YAG laser, the weldability of binary nickel-titanium shape memory alloys containing 50.0 and 48.5 at.-% Ti respectively was investigated. By tensile tests within a temperature range of -80 C to +200 C the mechanical properties of the laser welded joints were examined. Changes in the transformation behaviour were detected by calorimetric measurements (DSC method). The stress-strain behaviour was attributed to the microstructure of the welds, revealed by optical microscopy and transmission electron microscopy (TEM). Using a scanning electron microscope (SEM), the mechanisms of failure were examined. Joints of the martensitic Ti-rich alloy were brittle, showing an ultimate tensile strength of 600 MPa, corresponding to half of the value of the base material. The reduction in strength was explained by the formation of Ti{sub 2}Ni precipitations along grain boundaries in the weld. Since the welds still exhibited twin deformation, pseudoplastic strains of 7% were achieved. Ultimate strength data showed a very low scatter. Therefore it was possible to use the shape memory effect up to a strain of 6% without failure. After a total elongation to 6% strain, the laser welded joints showed a free recovery with an amnesia of 0.3%. The shape memory effect was shown to be retained in the laser welded joints. 154 refs.

  19. A study on the shape memory characteristics of Ti-Ni50-x-Pdx alloys

    International Nuclear Information System (INIS)

    Lee, H. W.; Chun, B. S.; Oh, S. J.; Kuk, I.H.

    1991-01-01

    The shape memory characteristics in TiNi alloys are greatly effected by the alloy composition and heat treatment condition. The present work was aimed to investigate the effect of Pd x (x=5,10,15,20) addition on the shape memory chracteristics of TiNi alloys by means of electrical resistance measurement. X-ray diffraction, differential scanning calorimetry and electron dispersive analysis X-ray measurement. The results obtained from this study are as follows; 1. The martensitic transformation start temperature, Ms of Ti-Ni 50-x -Pd x alloys decreased considerably with the increase of Pd content up to 10at%, whereas increased largely with the increase of Pd content in the alloys with Pd content more than 15at%. 2. The Ms temperature of Ti-Ni 50-x -Pd x alloys with cold working was significantly lower than that of the fully annealed alloys because high density dislocation has been introduced by the cold working which suppressed the martensitic transformation. (Author)

  20. 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.

  1. Cu-Al-Ni Shape Memory Single Crystal Wires with High Transformation Temperature

    Science.gov (United States)

    Hautcoeur, Alain; Fouché, Florian; Sicre, Jacques

    2016-01-01

    CN-250X is a new material with higher performance than Nickel-Titanium Shape Memory Alloy (SMA). For space mechanisms, the main disadvantage of Nickel-Titanium Shape Memory Alloy is the limited transformation temperature. The new CN-250X Nimesis alloy is a Cu-Al-Ni single crystal wire available in large quantity because of a new industrial process. The triggering of actuators made with this Cu-Al-Ni single crystal wire can range from ambient temperature to 200 C in cycling and even to 250 C in one-shot mode. Another advantage of CN-250X is a better shape recovery (8 to 10%) than Ni-Ti (6 to 7%). Nimesis is the first company able to produce this type of material with its new special industrial process. A characterization study is presented in this work, including the two main solicitation modes for this material: tensile and torsion. Different tests measure the shape recovery of Cu-Al-Ni single crystals wires during heating from room temperature to a temperature higher than temperature of end of martensitic transformation.

  2. Shape memory behavior of high strength NiTiHfPd polycrystalline alloys

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  3. Martensitic transformation behavior and shape memory properties of Ti-Ni-Pt melt-spun ribbons

    International Nuclear Information System (INIS)

    Inamura, Tomonari; Takahashi, Yohei; Hosoda, Hideki; Wakashima, Kenji; Nagase, Takeshi; Nakano, Takayoshi; Umakoshi, Yukichi; Miyazaki, Shuichi

    2006-01-01

    Martensitic transformation behavior and shape memory properties of a Ti 50 Ni 40 Pt 10 (TiNiPt) melt-spun ribbon fabricated by a single roll melt-spinning technique were characterized. The constituent phases of the as-spun ribbon were B2 (parent phase) and B19 (martensite phase) at room temperature. The B2-B19 martensitic transformation temperatures of the as-spun ribbon were 100K higher than those of the bulk-material with the same chemical composition. The martensitic transformation temperatures of the as-spun ribbon were decreased with increasing the temperature of the heat-treatment made after the melt-spinning. The as-spun ribbon and the heat-treated ribbons exhibited shape recovery by heating and/or pseudoelasticity. The martensitic transformation temperatures determined from the temperature dependence of the 0.2% flow stress of the pseudoelastic deformation were in good agreement with those of B2-B19 martensitic transformation determined by DSC. It was confirmed that the observed shape recovery and pseudoelasticity are shape memory effect and superelasticity due to the B2-B19 martensitic transformation. Shape memory effect and superelasticity of melt-spun TiNiPt alloy were found to appear at higher temperatures compared to those of Bulk-material with the same composition. (author)

  4. Fabrication and thermal characterization of amorphous and nanocrystalline Al{sub 9}FeNi/Al{sub 3}Ti compound

    Energy Technology Data Exchange (ETDEWEB)

    Tavoosi, Majid, E-mail: ma.tavoosi@gmail.com

    2017-01-15

    In this study, the fabrication and structural characterization of amorphous/nanocrystalline Al{sub 9}FeNi/Al{sub 3}Ti phase has been performed. In this regards, milling and annealing processes were applied on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} (at. %) powder mixture for different periods of time. The prepared samples were characterized using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) and differential scanning calorimetery (DSC). According to the results, supersaturated solid solution, nanocrystalline Al{sub 9}FeNi/Al{sub 3}Ti (with average crystallite size of about 7 nm) and amorphous phases indicated three different microstructures which can be formed in Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} system during milling process. The formed supersaturated solid solution and amorphous phases were unstable and transformed to Al{sub 9}FeNi/Al{sub 3}Ti intermetallic compound during annealing process. It is shown that, Al{sub 9}FeNi phase in Al{sub 9}FeNi/Al{sub 3}Ti intermetallic compound can decompose into Al{sub 3}Ni, Al{sub 13}Fe{sub 4} and liquid phases during a reversible peritectic reaction at 809 °C. - Highlights: • We study the effect of milling process on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} alloy. • We study the effect of annealing on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} supersaturated solid solution phase. • We study the effect of annealing on Al{sub 80}Fe{sub 10}Ti{sub 5}Ni{sub 5} amorphous phase. • We study the thermal behaviour of Al{sub 9}FeNi/Al{sub 3}Ti compound.

  5. Thermomechanical model for NiTi shape memory wires

    Czech Academy of Sciences Publication Activity Database

    Frost, Miroslav; Sedlák, Petr; Sippola, M.; Šittner, Petr

    2010-01-01

    Roč. 19, č. 9 (2010), s. 1-10 ISSN 0964-1726 R&D Projects: GA MŠk(CZ) 1M06031; GA ČR(CZ) GA106/09/1573; GA ČR(CZ) GP106/09/P302; GA ČR GAP108/10/1296 Institutional research plan: CEZ:AV0Z20760514; CEZ:AV0Z10100520 Keywords : shape memory alloys * modeling * proportional loading Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.094, year: 2010 http://apps.isiknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=3&SID=U2fe5mHN9p3gHClCdF1&page=1&doc=1

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

    International Nuclear Information System (INIS)

    Miyazaki, Shuichi; Ishida, Akira.

    1994-01-01

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

  7. Neutron diffraction study of dense-Kondo compound CeNi2Al5

    International Nuclear Information System (INIS)

    Munoz, A.; Givord, F.; Boucherie, J.X.; Flouquet, J.; Isikawa, Y.; Mizushima, T.; Sakurai, J.; Mori, K.; Oliveira, I.S.

    1993-01-01

    Intermetallic CeNi 2 Al 5 is a dense-Kondo compound with a magnetic transition temperature at 2.6 K. We have carried out a neutron diffraction measurement to study a magnetic structure of CeNi 2 Al 5 using a powder sample and a single crystalline sample. It is found that the magnetic structure is an incommensurate sinusoidal one with a propagation vector k = (0.5, 0.405, 0.083) and that the amplitude of magnetic moment is 1.54 μ Β and the direction of magnetic moment is declined 8 deg. from the b-axis toward the a-axis. (authors). 3 refs., 2 figs

  8. Molecular dynamics simulation of radiation-induced amorphization of the ordered compound NiZr2

    International Nuclear Information System (INIS)

    Devanathan, R.; Meshii, M.

    1992-12-01

    We have studied the electron irradiation-induced amorphization of the ordered intermetallic compound NiZr 2 by molecular dynamics simulations in conjunction with embedded-atom potentials. Randomly chosen Frenkel pairs and chemical disorder were introduced into the system in separate processes. In both cases, the energy and volume of the system rose above the corresponding levels of a quenched liquid and the calculated diffraction patterns indicated the occurrence of a crystalline-to-amorphous transition. In addition, the average shear elastic constant fell to about 50% of its value in the perfect crystal and the system became elastically isotropic. These results indicate that NiZr 2 can be amorphized by chemical disorder as well as Frenkel pairs and are in good agreement with experimental observations

  9. Characterization of the laser gas nitrided surface of NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Cui, Z.D.; Man, H.C.; Yang, X.J.

    2003-01-01

    Owing to its unique properties such as shape memory effects, superelasticity and radiopacity, NiTi alloy is a valuable biomaterial for fabricating implants. The major concern of this alloy for biological applications is the high atomic percentage of nickel in the alloy and the deleterious effects to the body by the corrosion and/or wears products. In this study, a continuous wave Nd-YAG laser was used to conduct laser gas nitriding on the substrate of NiTi alloy. The results show that a continuous and crack-free thin TiN layer was produced in situ on the NiTi substrate. The characteristics of the nitrided surface layer were investigated using SEM, XRD, XPS and AAS. No nickel signal was detected on the top surface of the laser gas nitrided layer. As compared with the mechanical polished NiTi alloy, the nickel ion release rate out of the nitrided NiTi alloy decreased significantly in Hanks' solution at 37 deg. C, especially the initial release rate

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

    NARCIS (Netherlands)

    Zhao, L.

    1997-01-01

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

  11. 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.

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

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  13. The effect of addition of various elements on properties of NiTi-based shape memory alloys for biomedical application

    Science.gov (United States)

    Kök, Mediha; Ateş, Gonca

    2017-04-01

    In biomedical applications, NiTi and NiTi-based alloys that show their shape memory effects at body temperature are preferred. In this study, the purpose is to produce NiTi and NiTi-based alloys with various chemical rates and electron concentrations and to examine their various physical properties. N45Ti55, Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Sn, Co) alloys were produced in an arc melter furnace in this study. After the homogenization of these alloys, the martensitic phase transformation temperatures were determined with differential-scanner calorimeter. The transformation temperature was found to be below the 37 ° C (body temperature) in Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Co) alloys; and the transformation temperature of the N45Ti55, Ni48Ti51Sn alloys was found to be over 37 ° C . Then, the micro and crystal structure analyses of the alloys were made, and it was determined that Ni45Ti50Cr2.5Cu2.5, Ni48Ti51X (X=Mn, Co) alloys, which were in austenite phase at room temperature, included B2 (NiTi) phase and Ti2Ni precipitation phase, and the alloys that were in the martensite phase at room temperature included B19ı (NiTi) phase and Ti2Ni phase. The common phase in both alloy groups is the Ti2Ni phase, and this type of phase is generally seen in NiTi alloys that are rich in titanium (Ti-rich).

  14. 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.

  15. TiNi shape memory alloys: effects of the fabrication route, the oxygen content and the zirconium or hafnium additions on the metallurgical characteristics and the thermomechanical properties

    International Nuclear Information System (INIS)

    Olier, P.

    1996-01-01

    In order to promote the development of Ti-Ni shape memory alloys, we have studied the correlation between the fabrication route, the chemical composition (O 2 content, Zr or Hf additions), the metallurgical characteristics and the thermomechanical properties. A conventional sintering does not allow to obtain a homogeneous compound of pure Ti 50 Ni 50 alloy because of the occurrence of Kirkendall porosities which act as a diffusion barrier. An original process including combustion synthesis and hot-extrusion was successfully developed. Resulting products exhibit a smaller grain size (15-20μm) and an enhanced workability in comparison with products obtained by arc-melting and subsequent hot rolling. The presence of oxygen in equiatomic Ti-Ni alloy induces the oxide precipitation of Ti 4 Ni 2 O x type (with x ≤ 1). The precipitated particle fraction is proportional to the oxygen nominal content of the alloy. We show that the decrease of the transformation temperatures is correlated with the decrease of Ti in solid solution due to Ti 4 Ni 2 O precipitation. Moreover, we find that a fine and homogenous oxide dispersion is suitable to decrease the grain size during hot rolling and to enhance to the one way shape memory properties. An increase of the typical transformation temperatures is obtained through of Zr or Hf (in substitution to Ti). But, an increase of the hardness is measured, and consequently the workability of the ternary alloys becomes reduced. However, it is worthwhile to point out that a Ti 38 Ni 50 Hf 12 product obtained by arc melting and hot extrusion is able to fully recover an apparent plastic strain of more than 4% during tensile tests performed under special loading conditions. Such as behaviour is of great interest with respect to potential applications in a temperature range higher that 100 deg. C. (author)

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

    Science.gov (United States)

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

    2010-01-01

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

  17. Effect of grain size of parent phase on twinning modes of B19` martensite in an equiatomic Ti-Ni shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nishida, M. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Itai, I. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Kitamura, K. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Chiba, A. [Kumamoto Univ. (Japan). Dept. of Mater. Sci. and Resource Eng.; Yamauchi, K. [Tokin Corp., Sendai (Japan)

    1995-12-01

    The effect of grain size of B2 parent phase on the twinning modes of B19` martensite in a Ti-50.0 at% Ni shape memory alloy has been studied. The grain size of parent phase was controlled from submicrons to several ten microns by cold-rolling and subsequent annealing. (001) compound twins were dominantly observed in the grain less than 4 {mu}m in diameter, although the (001) compound twinning did not give a solution to the phenomenological crystallographic theory. The triangular self-accommodating morphology of the martensite variants consisting of left angle 011 right angle Type II twins which were theoretically and experimentally recognized as a lattice invariant shear of the present transformation appeared in the whole grain more than 4 {mu}m in diameter. The formation mechanism of the (001) compound twinning in the fine grain is also discussed. (orig.).

  18. Magnetic order of Y{sub 3}NiSi{sub 3}-type R{sub 3}NiSi{sub 3} (R=Gd–DY) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Faculty of Geology, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600036 (India); Malik, S.K.; Quezado, S. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil); Yao, Jinlei; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Nigam, A.K. [Tata Institute of Fundamental Research, Mumbai 400005 (India); Isnard, O. [Université Grenoble Alpes, Inst NEEL, BP166, F-38042 Grenoble (France); CNRS, Institut NEEL, 25 rue des martyrs, F-38042 Grenoble (France)

    2016-01-15

    Magnetic measurements and neutron powder diffraction investigations on the Y{sub 3}NiSi{sub 3}-type R{sub 3}NiSi{sub 3} compounds (R=Gd, Tb, Dy) reveal their complex antiferromagnetic ordering. Magnetic measurements on Gd{sub 3}NiSi{sub 3}, Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} indicate antiferromagnetic-like transition at temperatures 260 K, 202 K and 140 K, respectively. Also, the Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} compounds show spin-reorientation transition at 132 K and 99 K, respectively. Below the spin-reorientation transition, the isothermal magnetization curves indicate the metamagnetic-like behavior of Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3}. The magnetocaloric effect of Dy{sub 3}NiSi{sub 3} is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of −1.2 J/kg K and −1.1 J/kg K for a field change of 50 kOe near 146 K and 92 K, respectively. The neutron diffraction studies of Tb{sub 3}NiSi{sub 3} suggest the magnetic ordering of the Tb2 4j sublattice and no magnetic ordering of the Tb1 2a sublattice. Tb{sub 3}NiSi{sub 3} transforms from the high temperature paramagnetic state to the commensurate high-temperature a- and c-axis antiferromagnet of I′2/m magnetic space group below 250 K. Below 150 K, the high-temperature antiferromagnet transforms into the low-temperature a-, b- and c-axis antiferromagnet of I′i magnetic space group. At 1.5 K, the terbium magnetic moment in Tb2 sublattice and its a-, b- and c-axis components reach the values of M{sub Tb2}=8.2(1) μ{sub B}, M{sub aTb2}=5.9(1) μ{sub B}, M{sub bTb2}=4.3(2) μ{sub B} and M{sub cTb2}=3.7(2) μ{sub B}, respectively. - Highlights: • Gd{sub 3}NiSi{sub 3}, Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} have Neel points of 260. 202 and 140 K. • Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} show spin-reorientation transition at 132 and 99 K. • Tb{sub 3}NiSi{sub 3} exhibits the commensurate magnetic ordering of Tb2 4j sublattice

  19. Hydrogen storage in Mg-Ni-Fe compounds prepared by melt spinning and ball milling

    Energy Technology Data Exchange (ETDEWEB)

    Palade, P. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy); National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Sartori, S. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy); Maddalena, A. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy); Principi, G. [Settore Materiali, Dipartimento di Ingegneria Meccanica, Universita di Padova, via Marzolo 9, 35131 Padova (Italy)]. E-mail: giovanni.principi@unipd.it; Lo Russo, S. [Dipartimento di Fisica, Universita di Padova, Via Marzolo 8, 35131 Padova (Italy); Lazarescu, M. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Schinteie, G. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Kuncser, V. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Filoti, G. [National Institute for Physics of Materials, Atomistilor 105 bis, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania)

    2006-05-18

    Magnesium-rich Mg-Ni-Fe intermetallic compounds have been prepared by two different routes: (a) short time ball milling of ribbons obtained by melt spinning; (b) long time ball milling of a mixture of MgH{sub 2}, Ni and Fe powders. The first type of samples displays an hydrogen desorption kinetics better than the second one. Pressure composition isotherm measurements exhibit for both type of samples two plateaux, the lower and wider corresponding to the MgH{sub 2} phase and the upper and shorter corresponding to the Mg{sub 2}NiH{sub 4} phase. The presence of the two types of hydrides is confirmed by X-ray diffraction analysis. Moessbauer spectroscopy shows that in melt spun and subsequently milled samples iron is mainly in a disordered structure and segregates after hydrogenation, while in directly milled powders remains mainly unalloyed. After multiple hydrogen absorption/desorption cycles the main part of iron is in metallic state in samples of both types, those of first type preserving better hydrogen desorption kinetics.

  20. Magnetoresistance in ferromagnetic shape memory alloy NiMnFeGa

    International Nuclear Information System (INIS)

    Liu, Z.H.; Ma, X.Q.; Zhu, Z.Y.; Luo, H.Z.; Liu, G.D.; Chen, J.L.; Wu, G.H.; Zhang Xiaokai; Xiao, John Q.

    2011-01-01

    The magnetoresistance (MR){=[R(H)-R(0)]/R(0)} 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 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 (ρ perpendicular >ρ || ) 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 C . → Conventional AMR behaviors due to the spin-orbital coupling are observed in NiMnFeGa single crystal and Ni 2 FeGa ribbon samples at low temperatures.

  1. Stress-temperature phase diagram of a ferromagnetic Ni-Mn-Ga shape memory alloy

    International Nuclear Information System (INIS)

    Chernenko, V.A.; Pons, J.; Cesari, E.; Ishikawa, K.

    2005-01-01

    A sequence of thermally and stress-induced intermartensitic transformations has been found in a Ni 52.0 Mn 24.4 Ga 23.6 single crystal, which have been confirmed by transmission electron microscopy through in situ cooling experiments. The stress-strain-temperature behavior under compression along the P and P crystallographic directions has also been studied for this compound and a stress-temperature phase diagram has been established

  2. Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

    2007-01-01

    High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  4. 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.

  5. NiTi shape memory via solid-state nudge-elastic band

    Science.gov (United States)

    Zarkevich, Nikolai A.; Johnson, Duane D.

    2014-03-01

    We determine atomic mechanisms of the shape memory effect in NiTi from a generalized solid-state nudge elastic band (SSNEB) method. We consider transformation between the austenite B2 and the ground-state base-centered orthorhombic (BCO) structures. In these pathways we obtain the R-phase and discuss its structure. We confirm that BCO is the ground state, and determine the pathways to BCO martensite, which dictate transition barriers. While ideal B2 is unstable, we find a B2-like NiTi high-temperature solid phase with significant local displacement disorder, which is B2 on average. This B2-like phase appears to be entropically stabilized. This work is supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Science and Engineering. Ames Laboratory is operated for the U.S. DOE by Iowa State University under contract DE-AC02-07CH11358.

  6. On the shock response of the shape memory alloy, NiTi

    International Nuclear Information System (INIS)

    Millett, J.C.F.; Bourne, N.K.; Stevens, G.S.; Gray, G.T. III

    2002-01-01

    There has been recent interest in the behaviour of the shape-memory alloy NiTi since it undergoes a stress-induced phase change at a low stress value. It has been additionally noted that the NiTi does not appear to exhibit a Hugoniot elastic limit (HEL) in the way normally associated with other metals. In order to investigate the possible mechanisms operating to give rise to these effects, a series of plate impact experiments have been conducted in order to probe the material's response to shock. In particular attention has been paid to determination of the material Hugoniot in order to ascertain whether the observed features of the response may be explained. A series of other shots where shaped waves are applied are described in order to probe the lower rate response

  7. Surface mechanical attrition treatment induced phase transformation behavior in NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Hu, T.; Wen, C.S.; Lu, J.; Wu, S.L.; Xin, Y.C.; Zhang, W.J.; Chu, C.L.; Chung, J.C.Y.; Yeung, K.W.K.; Kwok, D.T.K.; Chu, Paul K.

    2009-01-01

    The phase constituents and transformation behavior of the martensite B19' NiTi shape memory alloy after undergoing surface mechanical attrition treatment (SMAT) are investigated. SMAT is found to induce the formation of a parent B2 phase from the martensite B19' in the top surface layer. By removing the surface layer-by-layer, X-ray diffraction reveals that the amount of the B2 phase decreases with depth. Differential scanning calorimetry (DSC) further indicates that the deformed martensite in the sub-surface layer up to 300 μm deep exhibits the martensite stabilization effect. The graded phase structure and transformation behavior in the SMATed NiTi specimen can be attributed to the gradient change in strain with depth.

  8. Tensile and superelastic fatigue characterization of NiTi shape memory cables

    Science.gov (United States)

    Sherif, Muhammad M.; Ozbulut, Osman E.

    2018-01-01

    This paper discusses the tensile response and functional fatigue characteristics of a NiTi shape memory alloy (SMA) cable with an outer diameter of 5.5 mm. The cable composed of multiple strands arranged as one inner core and two outer layers. The results of the tensile tests revealed that the SMA cable exhibits good superelastic behavior up to 10% strain. Fatigue characteristics were investigated under strain amplitudes ranging from 3% to 7% and a minimum of 2500 loading cycles. The evolutions of maximum tensile stress, residual strains, energy dissipation, and equivalent viscous damping under a number of loading cycles were analyzed. The fracture surface of a specimen subjected to 5000 loading cycles and 7% strain was discussed. Functional fatigue test results indicated a very high superelastic fatigue life cycle for the tested NiTi SMA cable.

  9. Microstructure and mechanical behavior of a shape memory Ni-Ti bi-layer thin film

    Energy Technology Data Exchange (ETDEWEB)

    Mohri, Maryam [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Nili-Ahmadabadi, Mahmoud, E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Ivanisenko, Julia [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Schwaiger, Ruth [Karlsruhe Institute of Technology, Institute for Applied Materials, 76021 Karlsruhe (Germany); Hahn, Horst; Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

    2015-05-29

    Two different single-layers and a bi-layer Ni-Ti thin films with chemical compositions of Ni{sub 45}Ti{sub 50}Cu{sub 5}, Ni{sub 50.8}Ti{sub 49.2} and Ni{sub 50.8}Ti{sub 49.2}/Ni{sub 45}Ti{sub 50}Cu{sub 5} (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy were deposited on Si (111) substrates using DC magnetron sputtering. The structures, surface morphology and transformation temperatures of annealed thin films at 500 °C for 15 min and 1 h were studied using grazing incidence X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the austenitic structure of the Ni{sub 50.8}Ti{sub 49.2} and martensitic structure of the Ni{sub 45}Ti{sub 50}Cu{sub 5} thin films while the bi-layer was composed of austenitic and martensitic thin films. TEM study revealed that copper encourages crystallization in the bi-layer such that crystal structure containing nano-precipitates in the Ni{sub 45}Ti{sub 50}Cu{sub 5} layer was detected after 15 min annealing while the Ni{sub 50.8}Ti{sub 49.2} layer crystallized after 60 min at 500 °C. Furthermore, after annealing at 500 °C for 15 min, a precipitate free zone and thin layer amorphous were observed closely to the interface in the top layer. The bi-layer was completely crystallized at 500 °C for 1 h and the orientation of the Ni-rich precipitates indicated a stress gradient in the bi-layer. The bi-layer thin film showed different transformation temperatures and mechanical behavior from the single-layers. The developed bi-layer has different phase transformation temperatures, the higher temperatures of shape memory effect and lower temperature of pseudo-elastic behavior compared to the single-layers. Also, the bi-layer thin film exhibited a combined pseudo-elastic behavior and shape memory effect with a reduced

  10. Effect of cold rolling on fatigue crack propagation of TiNi/A16061 shape memory composite

    International Nuclear Information System (INIS)

    Lee, Jin Kyung; Lee, Sang Pill; Park, Young Chul; Lee, Kyu Chang; Cho, Youn Ho; Lee, Joon Hyun

    2005-01-01

    TiNi alloy fiber was used to recover the original shape of materials using its shape memory effect. The shape memory alloy plays an important role within the metal matrix composite. The shape memory alloy can control the crack propagation in metal matrix composite, and improve the tensile strength of the composite. In this study, TiNi/A16061 Shape Memory Alloy(SMA) composite was fabricated by hot press method, and pressed by a roller for its strength improvement. The four kinds of specimens were fabricated with 0%, 3.2%, 5.2% and 7% volume fraction of TiNi alloy fiber, respectively. A fatigue test has performed to evaluate the crack initiation and propagation for the TiNi/A16061 SMA composite fabricated by this method. In order to study the shape memory effect of the TiNi alloy fiber, the test has also done under both conditions of the room temperature and high temperature. The relationship between the crack growth rate and the stress intensity factor was clarified for the composite, and the cold rolling effect was also studied

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

    International Nuclear Information System (INIS)

    He Zhirong; Liu Manqian

    2011-01-01

    Highlights: → New shape memory alloy (SMA) - Ti-50.8Ni-0.5V SMA. → The evolution laws of transformation types of annealed Ti-50.8Ni-0.5V SMA. → The evolution laws of transformation types of aged Ti-50.8Ni-0.5V SMA. → The effect laws of annealing on transformation temperature and hysteresis of the alloy. → 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 → R/R → A (A - parent phase, R - R phase) type one-stage reversible transformation occurs in 350-400 deg. C annealed alloy, the A → R → M/M → R → A (M - martensite) type two-stage transformation occurs in 450-500 deg. C annealed alloy, the A → R → M/M → A type transformation occurs in 550 deg. C annealed alloy, and A → M/M → 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 → R/R → A, and that of 500 deg. C aged alloy is A → R → M/M → A, while that of 400 deg. C aged alloy changes from A → R/R → A to A → R → M/M → R → 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.

  12. Characterization of NiTi Shape Memory Damping Elements designed for Automotive Safety Systems

    Science.gov (United States)

    Strittmatter, Joachim; Clipa, Victor; Gheorghita, Viorel; Gümpel, Paul

    2014-07-01

    Actuator elements made of NiTi shape memory material are more and more known in industry because of their unique properties. Due to the martensitic phase change, they can revert to their original shape by heating when subjected to an appropriate treatment. This thermal shape memory effect (SME) can show a significant shape change combined with a considerable force. Therefore such elements can be used to solve many technical tasks in the field of actuating elements and mechatronics and will play an increasing role in the next years, especially within the automotive technology, energy management, power, and mechanical engineering as well as medical technology. Beside this thermal SME, these materials also show a mechanical SME, characterized by a superelastic plateau with reversible elongations in the range of 8%. This behavior is based on the building of stress-induced martensite of loaded austenite material at constant temperature and facilitates a lot of applications especially in the medical field. Both SMEs are attended by energy dissipation during the martensitic phase change. This paper describes the first results obtained on different actuator and superelastic NiTi wires concerning their use as damping elements in automotive safety systems. In a first step, the damping behavior of small NiTi wires up to 0.5 mm diameter was examined at testing speeds varying between 0.1 and 50 mm/s upon an adapted tensile testing machine. In order to realize higher testing speeds, a drop impact testing machine was designed, which allows testing speeds up to 4000 mm/s. After introducing this new type of testing machine, the first results of vertical-shock tests of superelastic and electrically activated actuator wires are presented. The characterization of these high dynamic phase change parameters represents the basis for new applications for shape memory damping elements, especially in automotive safety systems.

  13. Highly uniform and reliable resistive switching characteristics of a Ni/WOx/p+-Si memory device

    Science.gov (United States)

    Kim, Tae-Hyeon; Kim, Sungjun; Kim, Hyungjin; Kim, Min-Hwi; Bang, Suhyun; Cho, Seongjae; Park, Byung-Gook

    2018-02-01

    In this paper, we investigate the resistive switching behavior of a bipolar resistive random-access memory (RRAM) in a Ni/WOx/p+-Si RRAM with CMOS compatibility. Highly unifrom and reliable bipolar resistive switching characteristics are observed by a DC voltage sweeping and its switching mechanism can be explained by SCLC model. As a result, the possibility of metal-insulator-silicon (MIS) structural WOx-based RRAM's application to Si-based 1D (diode)-1R (RRAM) or 1T (transistor)-1R (RRAM) structure is demonstrated.

  14. Transformation lines in an Fe-Cr-Ni-Mn-Si polycrystalline shape memory alloy

    International Nuclear Information System (INIS)

    Tanaka, Kikuaki; Hayashi, Toshimitsu; Fischer, F.D.; Buchmayr, B.

    1994-01-01

    Transformation lines, the martensite/austenite start and finish conditions in the stress-temperature plane, are determined in an Fe-Cr-Ni-Mn-Si polycrystalline shape memory alloy with two different experimental procedures. The transformation lines are shown to be almost linear with nearly the same slope. The martensitic transformation zone and the reverse transformation zone do not coincide, and the reverse transformation zone is very wide; T Af -T As ∼ 180 K. The strong dependence on the preloading of the transformation lines, especially of the reverse transformation lines, is examined. (orig.)

  15. Mechanical properties and related substructure of TiNi shape memory alloys

    International Nuclear Information System (INIS)

    Filip, P.; Kneissl, A.C.

    1995-01-01

    The mechanical properties of binary near equiatomic TiNi shape memory alloys were investigated after different types of mechanical and heat treatments. The changes of deformation behaviour are explained on the basis of substructure differences after work hardening. The ''elastic moduli'' of both the high-temperature phase B2 and the martensite B19' as well as the ''easy stage of deformation'' are dependent on the work hardening intensity and these changes are related to the mobility of B2/B19' interfaces. The martensite changes its morphology after work hardening. In contrast to a twinned martensite, typical for annealed alloys, the internally slipped martensite was detected after work hardening. (orig.)

  16. Characterization of the Ni-45wt% Ti shape memory alloy rapidly solidified

    International Nuclear Information System (INIS)

    Anselmo, G.C.S.; Castro, W.B. de; Araujo, C.J. de

    2010-01-01

    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)

  17. The effect of hafnium content on the transformation temperatures of Ni49Ti51-xHfx shape memory alloys

    International Nuclear Information System (INIS)

    Angst, D.R.; Thoma, P.E.; Kao, M.Y.

    1995-01-01

    Ternary alloys of NiTiHf, having higher transformation temperatures than binary NiTi shape memory alloys, have been produced and analyzed. Beginning with a base composition of Ni 49 Ti 51 , Hf was substituted for Ti up to 30 atomic percent. Differential scanning calorimetry was used to determine the transformation temperatures of the as-cast alloys. The peak martensite temperature of the Ni 49 Ti 51 alloy was 69 C and increased to 525 C for the Ni 49 Ti 21 Hf 30 alloy. The peak austenite temperature of the Ni 49 Ti 51 alloy was 114 C and increased to 622 C for the Ni 49 Ti 21 Hf 30 alloy. An apparent minimum in the peak transformation temperatures occurred between 0 and 3 atomic percent Hf. Preliminary experiments were also conducted to determine the effect of thermomechanical processing on the shape memory properties of the Ni 49 Ti 41 Hf 10 . Data are presented on the effect of cold work and heat treatment on the transformation temperatures of this alloy. (orig.)

  18. Orientation dependence and tension/compression asymmetry of shape memory effect and superelasticity in ferromagnetic Co40Ni33Al27, Co49Ni21Ga30 and Ni54Fe19Ga27 single crystals

    International Nuclear Information System (INIS)

    Chumlyakov, Y.; Panchenko, E.; Kireeva, I.; Karaman, I.; Sehitoglu, H.; Maier, H.J.; Tverdokhlebova, A.; Ovsyannikov, A.

    2008-01-01

    In the present study the effects of crystal axis orientation, stress state (tension/compression) and test temperature on shape memory effect and superelasticity of Ni 54 Fe 19 Ga 27 (I), Co 40 Ni 33 Al 27 (II), Co 49 Ni 21 Ga 30 (III) (numbers indicate at.%) single crystals were investigated. The shape memory effect, the start temperature of superelasticity T 1 and the mechanical hysteresis Δσ were found to be dependent on crystal axis orientation and stress state. Superelasticity was observed at T 1 = A f (A f , reverse transformation-finish temperature) in tension/compression for [0 0 1]-oriented Ni-Fe-Ga crystals and in compression for [0 0 1]-oriented Co-Ni-Ga crystals, which all displayed a small mechanical hysteresis (Δσ ≤ 30 MPa). An increase in Δσ of up to 90 MPa in the Co-Ni-Al and the Co-Ni-Ga crystals lead to stabilization of the stress-induced martensite, and an increase in to T 1 = A f + Δ. The maximal value of Δ (75 K) was found in [0 0 1]-oriented Co-Ni-Al crystals in tension. A thermodynamic criterion describing the dependencies of the start temperature of superelasticity T 1 on crystal axis orientation, stress state and the magnitude of mechanical hysteresis is discussed

  19. B2 intermetallic compounds of Zr. New class of the shape memory alloys

    International Nuclear Information System (INIS)

    Koval, Yu.N.; Delaey, L.; Jang, W.Y.

    1995-01-01

    It is known that the B2 equiatomic intermetallic compounds of Zr (ZrCo-based) undergo a martensitic transformation (MT) with wide temperature hysteresis. It was found that the MT is accompanied by the perfect shape memory effect (SME) for ZrCu and ZrRh. In this report we represent the results of structural analysis, electrical resistivity, calorimetric and SME measurements for ZrCu- and ZrCo-based compounds. Interrelation between structural, thermodynamical parameters of MT and SME in this alloys will be described. The shape memory aspects of this potential alloys for the application at high temperatures will be discussed. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-02-15

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

  1. Magnetic ordering of YPd{sub 2}Si-type HoNi{sub 2}Si and ErNi{sub 2}Si compounds

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow, 119992 (Russian Federation); Isnard, O. [CNRS, Insitut. Néel, 25 Rue Des Martyrs BP166 x, F-38042 Grenoble (France); Université Grenoble Alpes, Inst. Néel, F-38042 Grenoble (France); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600 036 (India); Quezado, S.; Malik, S.K. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil)

    2016-12-01

    Magnetic properties of YPd{sub 2}Si-type HoNi{sub 2}Si and ErNi{sub 2}Si were investigated via neutron diffraction and magnetisation measurements. HoNi{sub 2}Si and ErNi{sub 2}Si show ferromagnetic-like ordering at T{sub C} of 9 K and 7 K, respectively. The paramagnetic Weiss temperatures are 9 K and 11 K and the effective magnetic moments are 10.76 μ{sub B}/fu and 9.79 μ{sub B}/fu for HoNi{sub 2}Si and ErNi{sub 2}Si compounds, respectively. The HoNi{sub 2}Si and ErNi{sub 2}Si are soft ferromagnets with saturation magnetization of 8.1 μ{sub B}/fu and 7.5 μ{sub B}/fu, respectively at 2 K and in field of 140 kOe. The isothermal magnetic entropy change, ΔS{sub m}, has a maximum value of −15.6 J/kg·K at 10 K for HoNi{sub 2}Si and −13.9 J/kg·K at 6 K for ErNi{sub 2}Si for a field change of 50 kOe. Neutron diffraction study in zero applied field shows mixed ferromagnetic-antiferromagnetic ordering of HoNi{sub 2}Si at ~9 K and its magnetic structure is a sum of a-axis ferromagnetic F{sub a}, b-axis antiferromagnetic AF{sub b} and c-axis antiferrromagnetic AF{sub c} components of Pn′a2{sub 1}′={1, m_x′/[1/2, 1/2, 1/2], 2_y′/[0, 1/2, 0], m_z/[1/2, 0, 1/2]} magnetic space group and propagation vector K{sub 0}=[0, 0, 0]. The holmium magnetic moment reaches a value of 9.23(9) μ{sub B} at 1.5 K and the unit cell of HoNi{sub 2}Si undergoes isotropic contraction around the temperature of magnetic transition. - Graphical abstract: HoNi{sub 2}Si: mixed ferro-antiferromagnet (F{sub a}+AF{sub b}+AF{sub c}){sup K0} with Pn′a2{sub 1}′ magnetic space group and K{sub 0}=[0, 0, 0] propagation vector below 10 K. - Highlights: • Ferro-antiferromagnetic ordering is observed in HoNi{sub 2}Si at 9 K and in ErNi{sub 2}Si at 7 K. • HoNi{sub 2}Si is soft ferromagnet with ΔS{sub m} of −15.6 J/kg·K at 10 K in field of 0–50 kOe. • ErNi{sub 2}Si is soft ferromagnet with ΔS{sub m} of −13.9 J/kg·K at 6 K in field of 0–50 kOe. • HoNi{sub 2}Si shows mixed F

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

    International Nuclear Information System (INIS)

    Sethi, Brahmananda; Sarma, S.; Srinivasan, A.; Santra, S. B.

    2014-01-01

    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 45 Ni 25 Ga 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 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

  3. Behavior and effect of Ti2Ni phase during processing of NiTi shape memory alloy wire from cast ingot

    International Nuclear Information System (INIS)

    Bhagyaraj, J.; Ramaiah, K.V.; Saikrishna, C.N.; Bhaumik, S.K.; Gouthama

    2013-01-01

    Highlights: •Ti 2 Ni second phase particles forms in different sizes and shapes in cast ingot. •TEM evidences showed shearing/fragmentation of Ti 2 Ni during processing. •Matrix close to Ti 2 Ni experienced severe plastic deformation lead to amorphisation. •Ti 2 Ni interfaces were mostly faceted and assist in nucleation of martensite. •Heterogeneity of microstructure observed near to and away from Ti 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 2 Ni type SPPs in the matrix. In the cast alloy, the Ti 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Eichhorn, Tobias

    2011-12-09

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

  5. Compound words prompt arbitrary semantic associations in conceptual memory

    OpenAIRE

    Boutonnet, Bastien; McClain, Rhonda; Thierry, Guillaume

    2014-01-01

    Linguistic relativity theory has received empirical support in domains such as colour perception and object categorisation. It is unknown however, whether relations between words idiosyncratic to language impact nonverbal representations and conceptualisations. For instance, would one consider the concepts of horse and sea as related were it not for the existence of the compound seahorse? Here, we investigated such arbitrary conceptual relationships using a non-linguistic picture relatedness ...

  6. 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.

  7. Effect of Manganese on Microstructures and Solidification Modes of Cast Fe-Mn-Si-Cr-Ni Shape Memory Alloys

    Science.gov (United States)

    Peng, Huabei; Wen, Yuhua; Du, Yangyang; Yu, Qinxu; Yang, Qin

    2013-10-01

    We investigated microstructures and solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys to clarify whether Mn was an austenite former during solidification. Furthermore, we examined whether the Creq/Nieq equations (Delong, Hull, Hammer and WRC-1992 equations) and Thermo-Calc software® together with database TCFE6 were valid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni shape memory alloys. The results have shown that the solidification modes of Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni alloys changed from the F mode to the FA mode with increasing the Mn concentration. Mn is an austenite former during the solidification for the cast Fe-Mn-Si-Cr-Ni shape memory alloys. The Delong, Hull, Hammer, and WRC-1992 equations as well as Thermo-Calc software® together with database TCFE6 are invalid to predict the solidification modes of cast Fe-(13-27)Mn-5.5Si-8.5Cr-5Ni SMAs. To predict the solidification modes of cast Fe-Mn-Si-Cr-Ni alloys, a new Creq/Nieq equation should be developed or the thermodynamic database of Thermo-Calc software® should be corrected.

  8. Impurity levels and fatigue lives of pseudoelastic NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Rahim, M.; Frenzel, J.; Frotscher, M.; Pfetzing-Micklich, J.; Steegmüller, R.; Wohlschlögel, M.; Mughrabi, H.; Eggeler, G.

    2013-01-01

    In the present work we show how different oxygen (O) and carbon (C) levels affect fatigue lives of pseudoelastic NiTi shape memory alloys. We compare three alloys, one with an ultrahigh purity and two which contain the maximum accepted levels of C and O. We use bending rotation fatigue (up to cycle numbers >10 8 ) and scanning electron microscopy (for investigating microstructural details of crack initiation and growth) to study fatigue behavior. High cycle fatigue (HCF) life is governed by the number of cycles required for crack initiation. In the low cycle fatigue (LCF) regime, the high-purity alloy outperforms the materials with higher number densities of carbides and oxides. In the HCF regime, on the other hand, the high-purity and C-containing alloys show higher fatigue lives than the alloy with oxide particles. There is high experimental scatter in the HCF regime where fatigue cracks preferentially nucleate at particle/void assemblies (PVAs) which form during processing. Cyclic crack growth follows the Paris law and does not depend on impurity levels. The results presented in the present work contribute to a better understanding of structural fatigue of pseudoelastic NiTi shape memory alloys

  9. Thermomechanical behavior of Ti-rich NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Paula, A.S.; Mahesh, K.K.; Santos, C.M.L. dos; Braz Fernandes, F.M.; Costa Viana, C.S. da

    2008-01-01

    Phase transformations associated with shape memory effect in nickel-titanium (NiTi) alloys can be one-stage, B19' (martensite) ↔ B2 (austenite), two-stage including an intermediate R-phase stage, or multiple-stage depending on the thermal and/or mechanical history of the alloy. In the present paper, we highlight the effect of (i) deformation by cold-rolling (from 10% to 40% thickness reduction) and (ii) final annealing on the transformation characteristics of a Ti-rich NiTi shape memory alloy. For this purpose, one set of samples initially heat treated at 773 K followed by cold-rolling (10-40% thickness reduction), has been further heat treated at various temperatures between 673 and 1073 K. Another sample was subjected to heat treatment at 1040 K for 300 s followed by hot rolling (50%) after cooling in air to 773 K and water quenching to room temperature (T room ). Phase transformations were studied using differential scanning calorimetry, electrical resistivity measurements and in situ X-ray diffraction. A specific pattern of transformation sequences is found as a result of combination of the competing effects due to mechanical-working and annealing

  10. Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

    Science.gov (United States)

    Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

    2018-01-01

    Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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 Ni 19.5 Ti 50.5 Pd 25 Pt 5 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. (paper)

  12. Characterisation of melt spun Ni-Ti shape memory Ribbons' microstructure

    Science.gov (United States)

    Mehrabi, Kambiz; Brunčko, Mihael; Kneissl, Albert C.; Čolič, Miodrag; Stamenković, Dragoslav; Ferčec, Janko; Anžel, Ivan; Rudolf, Rebeka

    2012-06-01

    NiTi alloys are the most technologically important medical Shape Memory Alloys in a wide range of applications used in Orthopaedics, Neurology, Cardiology and interventional Radiology as guide-wires, self-expandable stents, stent grafts, inferior vena cava filters and clinical instruments. This paper discusses the use of rapid solidification by the melt spinning method for the preparation of thin NiTi ribbons for medical uses. Generally, the application of rapid solidification via melt-spinning can change the microstructure drastically, which improves ductility and shape memory characteristics and leads to samples with small dimensions. As the increase in the wheel speed led to a reduced ribbon thickness, the cooling rate increased and, therefore, the martensitic substructure became finer. Furthermore, no transition from the crystalline phase to the amorphous phase was obtained by increasing the cooling rate, even at a wheel speed of 30 m/s. Specimens for our metallographic investigation were cut from the longitudinal cross sections of melt-spun ribbons. Conventional TEM studies were carried out with an acceleration voltage of 120 kV. Additionally, the chemical composition of the samples was examined with a TEM equipped with an EDX analyser. The crystallographic structure was determined using Bragg-Brentano x-ray diffraction with Cu-Kα radiation at room temperature.

  13. Laser Shock Wave-Assisted Patterning on NiTi Shape Memory Alloy Surfaces

    Science.gov (United States)

    Ilhom, Saidjafarzoda; Seyitliyev, Dovletgeldi; Kholikov, Khomidkohodza; Thomas, Zachary; Er, Ali O.; Li, Peizhen; Karaca, Haluk E.; San, Omer

    2018-03-01

    Shape memory alloys (SMAs) are a unique class of smart materials and they were employed in various applications in engineering, biomedical, and aerospace technologies. Here, we report an advanced, efficient, and low-cost direct imprinting method with low environmental impact to create thermally controllable surface patterns. Patterned microindents were generated on Ni50Ti50 (at. %) SMAs using an Nd:YAG laser with 1064 nm wavelength at 10 Hz. Laser pulses at selected fluences were focused on the NiTi surface and generated pressure pulses of up to a few GPa. Optical microscope images showed that surface patterns with tailorable sizes can be obtained. The depth of the patterns increases with laser power and irradiation time. Upon heating, the depth profile of SMA surfaces changed where the maximum depth recovery ratio of 30% was observed. Recovery ratio decreased and stabilized when the number of pulses and thus the well depth were further increased. A numerical simulation of pressure evolution in shape memory alloys showed a good agreement with the experimental results. The stress wave closely followed the rise time of the laser pulse to its peak value and initial decay. Rapid attenuation and dispersion of the stress wave were found in our simulation.

  14. Mechanical response of nitrogen ion implanted NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Kucharski, S.; Levintant-Zayonts, N.; Luckner, J.

    2014-01-01

    Highlights: • The effect of ion implantation process on shape memory alloy was investigated. • In the implantation process both surface layer and bulk material are modified. • The microstructure is modified and superelastic effect is destroyed in surface layer. • The parameters of superelastic phenomena are changed in bulk material. - Abstract: In the paper a change of material (mechanical) parameters of NiTi shape memory alloy subjected to ion implantation treatment is investigated. The spherical indentation tests in micro- and nano-scale and tension test have been performed to study an evolution of local superelastic effect in different volumes of nonimplanted and nitrogen ion implanted NiTi alloy. The differential scanning calorimetry has been applied to measure the change of characteristic temperatures due to ion implantation treatment. The structure of implanted material has been investigated using electron microscopy technique. It has been found that the ion implantation process changes the properties not only in a thin surface layer but also in bulk material. In the layer the pseudoelastic effect is destroyed, and in the substrate is preserved, however its parameters are changed. The characteristic phase transformation temperatures in substrate are also modified

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

    Czech Academy of Sciences Publication Activity Database

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

    2017-01-01

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

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

    OpenAIRE

    Tsai De-Chang; Chiang Chen-Hsueh

    2015-01-01

    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 processi...

  17. The elastocaloric effect of Ni50.8Ti49.2 shape memory alloys

    Science.gov (United States)

    Zhou, Min; Li, Yushuang; Zhang, Chen; Li, Shaojie; Wu, Erfu; Li, Wei; Li, Laifeng

    2018-04-01

    Solid-state cooling technologies are considered as possible alternatives for vapor compression cooling systems. The elastocaloric cooling (whose caloric effects are driven by uniaxial stress) technology, as an efficient and clean solid-state cooling technology, is receiving a great deal of attention very recently. Herein, a NiTi-based elastocaloric bulk material was reported. A large coefficient-of-performance of the material (COPmater) of 4.5 was obtained, which was even higher than that of other NiTi bulk materials. The temperature changes (ΔT) increased with increasing applied strain (ɛ), and reached 18 K upon loading and  -11 K upon unloading when the ɛ value increased to 4%. The high temperature changes were attributed to the large stress-induced entropy changes (the maximum ΔS σ value was 37 J kg-1 K-1). The temperature changes decreased with loading-unloading tensile cycles, and stabilized at 6.5 K upon loading and  -6 K upon unloading after tens of mechanical cycles. The Ni50.8Ti49.2 shape memory alloy showed great promise for application in solid-state refrigeration (or as heat pumps).

  18. Laser shock wave assisted patterning on NiTi shape memory alloy surfaces

    Science.gov (United States)

    Seyitliyev, Dovletgeldi; Li, Peizhen; Kholikov, Khomidkhodza; Grant, Byron; Karaca, Haluk E.; Er, Ali O.

    2017-02-01

    An advanced direct imprinting method with low cost, quick, and less environmental impact to create thermally controllable surface pattern using the laser pulses is reported. Patterned micro indents were generated on Ni50Ti50 shape memory alloys (SMA) using an Nd:YAG laser operating at 1064 nm combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generates pressure pulses up to 10 GPa on the surface was focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the NiTi surface. Scanning electron microscope (SEM) and optical microscope images of square pattern with different sizes were studied. One dimensional profile analysis shows that the depth of the patterned sample initially increase linearly with the laser energy until 125 mJ/pulse where the plasma further absorbs and reflects the laser beam. In addition, light the microscope image show that the surface of NiTi alloy was damaged due to the high power laser energy which removes the graphite layer.

  19. Oxidation Kinetics of a NiPtTi High Temperature Shape Memory Alloy

    Science.gov (United States)

    Smialek, James L.; Humphrey, Donald L.; Noebe, Ronald D.

    2007-01-01

    A high temperature shape memory alloy (HTSMA), Ni30Pt50Ti, with an M(sub s) near 600 C, was isothermally oxidized in air for 100 hr over the temperature range of 500 to 900 C. Parabolic kinetics were confirmed by log-log and parabolic plots and showed no indication of fast transient oxidation. The overall behavior could be best described by the Arrhenius relationship: k(sub p) = 1.64 x 10(exp 12)[(-250 kJ/mole)/RT] mg(sup 2)/cm(sup 4)hr. This is about a factor of 4 reduction compared to values measured here for a binary Ni47Ti commercial SMA. The activation energy agreed with most literature values for TiO2 scale growth measured for elemental Ti and other NiTi alloys. Assuming uniform alloy depletion of a 20 mil (0.5 mm) dia. HTSMA wire, approx. 1 percent Ti reduction is predicted after 20,000 hr oxidation at 500 C, but becomes much more serious at higher temperatures.

  20. Exploiting NiTi shape memory alloy films in design of tunable high frequency microcantilever resonators

    Science.gov (United States)

    Stachiv, I.; Sittner, P.; Olejnicek, J.; Landa, M.; Heller, L.

    2017-11-01

    Shape memory alloy (SMA) films are very attractive materials for microactuators because of their high energy density. However, all currently developed SMA actuators utilize martensitic transformation activated by periodically generated heating and cooling; therefore, they have a slow actuation speed, just a few Hz, which restricts their use in most of the nanotechnology applications such as high frequency microcantilever based physical and chemical sensors, atomic force microscopes, or RF filters. Here, we design tunable high frequency SMA microcantilevers for nanotechnology applications. They consist of a phase transforming NiTi SMA film sputtered on the common elastic substrate material; in our case, it is a single-crystal silicon. The reversible tuning of microcantilever resonant frequencies is then realized by intentionally changing the Young's modulus and the interlayer stress of the NiTi film by temperature, while the elastic substrate guarantees the high frequency actuation (up to hundreds of kHz) of the microcantilever. The experimental results qualitatively agree with predictions obtained from the dedicated model based on the continuum mechanics theory and a phase characteristic of NiTi. The present design of SMA microcantilevers expands the capability of current micro-/nanomechanical resonators by enabling tunability of several consecutive resonant frequencies.

  1. Electrochemical Properties of Ni 47 Ti 49 Co 4 Shape Memory Alloy in Artificial Urine for Urological Implant

    KAUST Repository

    Ahmed, Rasha A.

    2015-09-02

    © 2015 American Chemical Society. The corrosion performance of Ni47Ti49Co4 shape memory alloys (SMA) in artificial urine solution was evaluated in comparison with Ni51Ti49 alloy as reference, at 37°C and pH 5.6-6.4. SEM results revealed less pitting attack for Ni47Ti49Co4 SMA surface after immersion in artificial urine solution. The XRD analysis demonstrated the formation of passive film on Ni47Ti49Co4 SMA. The XPS analysis indicated that the film mainly consisted of O, Ti, Co, P, and a small amount of Ni, and the concentration of Ni ions release was greatly reduced compared to that of the Ni51Ti49 SMA. Linear polarization results illustrated that corrosion potential (Ecorr), corrosion current density (icorr), and ac polarization resistance (Rp) were affected greatly by alloying Co to Nitinol alloy. Our observations indicated that the corrosion resistance of the ternary alloy, Ni47Ti49Co4 SMA, offers superior corrosion resistance in artificial urine when compared to Ni51Ti49 SMA, which was suitable for medical applications.

  2. Electrochemical Properties of Ni 47 Ti 49 Co 4 Shape Memory Alloy in Artificial Urine for Urological Implant

    KAUST Repository

    Ahmed, Rasha A.

    2015-01-01

    © 2015 American Chemical Society. The corrosion performance of Ni47Ti49Co4 shape memory alloys (SMA) in artificial urine solution was evaluated in comparison with Ni51Ti49 alloy as reference, at 37°C and pH 5.6-6.4. SEM results revealed less pitting attack for Ni47Ti49Co4 SMA surface after immersion in artificial urine solution. The XRD analysis demonstrated the formation of passive film on Ni47Ti49Co4 SMA. The XPS analysis indicated that the film mainly consisted of O, Ti, Co, P, and a small amount of Ni, and the concentration of Ni ions release was greatly reduced compared to that of the Ni51Ti49 SMA. Linear polarization results illustrated that corrosion potential (Ecorr), corrosion current density (icorr), and ac polarization resistance (Rp) were affected greatly by alloying Co to Nitinol alloy. Our observations indicated that the corrosion resistance of the ternary alloy, Ni47Ti49Co4 SMA, offers superior corrosion resistance in artificial urine when compared to Ni51Ti49 SMA, which was suitable for medical applications.

  3. Observation of martensitic structure evolution in Cu-Al-Ni single crystals with shape memory effect under external load using photoacoustic microscopy

    International Nuclear Information System (INIS)

    Muratikov, K.L.; Glazov, A.L.; Nikolaev, V.I.; Pul'nev, S.A.

    2006-01-01

    Photoacoustic microscopy is applied to observe the surface structure of Cu-Al-Ni shape-memory single crystals in both the loaded and unloaded states. Visualizing the early stages of the loading-induced martensitic transformation in Cu-Al-Ni single crystals is demonstrated to be feasible. The photoacoustic images are distinguished to advantage from the corresponding optical images by a higher contrast between different phases of the Cu-Al-Ni shape-memory alloy [ru

  4. Magnetron sputtered Cu{sub 3}N/NiTiCu shape memory thin film heterostructures for MEMS applications

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Navjot; Choudhary, Nitin [Indian Institute of Technology Roorkee, Roorkee, Functional Nanomaterials Research Lab, Department of Physics and Centre of Nanotechnology (India); Goyal, Rajendra N. [Indian Institute of Technology, Roorkee, Department of Chemistry (India); Viladkar, S. [Indian Institute of Technology Roorkee, Roorkee, Functional Nanomaterials Research Lab, Department of Physics and Centre of Nanotechnology (India); Matai, I.; Gopinath, P. [Indian Institute of Technology, Roorkee, Centre for Nanotechnology (India); Chockalingam, S. [Indian Institute of Technology, Guwahati, Department of Biotechnology (India); Kaur, Davinder, E-mail: dkaurfph@iitr.ernet.in [Indian Institute of Technology Roorkee, Roorkee, Functional Nanomaterials Research Lab, Department of Physics and Centre of Nanotechnology (India)

    2013-03-15

    In the present study, for the first time, Cu{sub 3}N/NiTiCu/Si heterostructures were successfully grown using magnetron sputtering technique. Nanocrystalline copper nitride (Cu{sub 3}N with thickness {approx}200 nm) thin films and copper nanodots were subsequently deposited on the surface of 2-{mu}m-thick NiTiCu shape memory thin films in order to improve the surface corrosion and nickel release properties of NiTiCu thin films. Interestingly, the phase transformation from martensite phase to austenite phase has been observed in Cu{sub 3}N/NiTiCu heterostructures with corresponding change in texture and surface morphology of top Cu{sub 3}N films. Field emission scanning electron microscopy and atomic force microscope images of the heterostructures reveals the formation of 20-nm-sized copper nanodots on NiTiCu surface at higher deposition temperature (450 Degree-Sign C) of Cu{sub 3}N. Cu{sub 3}N passivated NiTiCu films possess low corrosion current density with higher corrosion potential and, therefore, better corrosion resistance as compared to pure NiTiCu films. The concentration of Ni released from the Cu{sub 3}N/NiTiCu samples was observed to be much less than that of pure NiTiCu film. It can be reduced to the factor of about one-ninth after the surface passivation resulting in smooth, homogeneous and highly corrosion resistant surface. The antibacterial and cytotoxicity of pure and Cu{sub 3}N coated NiTiCu thin films were investigated through green fluorescent protein expressing E. coli bacteria and human embryonic kidney cells. The results show the strong antibacterial property and non cytotoxicity of Cu{sub 3}N/NiTiCu heterostructure. This work is of immense technological importance due to variety of BioMEMS applications.

  5. Magnetization, shape memory and hysteresis behavior of single and polycrystalline FeNiCoTi

    International Nuclear Information System (INIS)

    Sehitoglu, H.; Efstathiou, C.; Maier, H.J.; Chumlyakov, Y.

    2005-01-01

    We report on the shape memory characteristics and magnetic behavior of polycrystalline and single crystalline FeNiCoTi. Predeforming the samples in the martensitic state and biasing of the martensite variants produced anisotropy in the magnetization behavior allowing the 'easy axis' to be identified as the 'a-axis' in the martensitic state. Based on these results, we provide an estimate of the magnetic anisotropy energy as 8.34x10 5 ergs/cm 3 . The results confirm the different magnetization behavior in the martensitic and austenitic states, and the shift in transformation temperatures upon application of a magnetic field. Shape memory strains near 2.5% are demonstrated under constant stress temperature cycling and upon heating at zero stress after deformation. We present a thermodynamics based theory that explains the origin of the hysteresis in this class of alloys emanating from the dissipation of energy due to plastic deformation. We predict the thermal hysteresis (135 K), and the shift in transformation temperature (14 K) with applied magnetic fields in agreement with the experimental results. The possibility of utilizing these classes of alloys as magnetic shape memory alloys is discussed

  6. A Two-Way Shape Memory Study on Ni-Rich NiTi Shape Memory Alloy by Combination of the All-Round Treatment and the R-Phase Transformation

    Science.gov (United States)

    Wu, Z. H.; Vokoun, D.; Leu, C. C.; Hu, C. T.

    2017-12-01

    Ni4Ti3 precipitates are formed in Ni-rich NiTi shape memory alloys (SMAs) after a certain heat treatment. Such a treatment then results in the changed phase transformation behavior of the alloy switching from the one-step reversible phase change B2 ↔ B19' to the two-step, B2 ↔ R ↔ B19', phase change. The present study reports a two-way shape memory (TWSM) due to an all-round treatment followed by an R-phase constraint aging at room temperature. The enhanced TWSM behavior was observed upon temperature cycling between 273 K (R-phase) and 77 K (B19' phase). The effect of various constraint strains in R-phase aging by employing different diameters of the constraint ring was studied. However, the TWSM effect due to constraining the R-phase will be eliminated after a temperature rise of specimen to the fully parent phase (373 K).

  7. A model compound (methyl oleate, oleic acid, triolein) study of triglycerides hydrodeoxygenation over alumina-supported NiMo sulfide

    NARCIS (Netherlands)

    Coumans, A.E.; Hensen, E.J.M.

    We studied hydrodeoxygenation of model compounds for vegetable oil into diesel-range hydrocarbons on a sulfided NiMo/γ-Al2O3 catalyst under trickle-flow conditions. Methyl oleate (methyl ester of oleic acid, a C18 fatty acid with one unsaturated bond in the chain) represented the C18 alkyl esters in

  8. DO{sub 22}-(Cu,Ni){sub 3}Sn intermetallic compound nanolayer formed in Cu/Sn-nanolayer/Ni structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu Lilin [School of Physics and Engineering, Sun Yat-Sen University, Guangzhou 510275 (China); Huang, Haiyou [Department of Mechanical Engineering, Hong Kong University of Science and Technology (HKUST) (Hong Kong); Hong Kong - Beijing Joint Research Center, HKUST Fok Ying Tung Graduate School, Nansha, Guangzhou (China); Fu Ran; Liu Deming [ASM Assembly Automation Ltd. (Hong Kong); Zhang Tongyi, E-mail: mezhangt@ust.h [Department of Mechanical Engineering, Hong Kong University of Science and Technology (HKUST) (Hong Kong); Hong Kong - Beijing Joint Research Center, HKUST Fok Ying Tung Graduate School, Nansha, Guangzhou (China)

    2009-11-03

    The present work conducts crystal characterization by High Resolution Transmission Electron Microscopy (HRTEM) on Cu/Sn-nanolayer/Ni sandwich structures associated with the use of Energy Dispersive X-ray (EDX) analysis. The results show that DO{sub 22}-(Cu,Ni){sub 3}Sn intermetallic compound (IMC) ordered structure is formed in the sandwich structures at the as-electrodeposited state. The formed DO{sub 22}-(Cu,Ni){sub 3}Sn IMC is a homogeneous layer with a thickness about 10 nm. The DO{sub 22}-(Cu,Ni){sub 3}Sn IMC nanolayer is stable during annealing at 250 deg. C for 810 min. The formation and stabilization of the metastable DO{sub 22}-(Cu,Ni){sub 3}Sn IMC nanolayer are attributed to the less strain energy induced by lattice mismatch between the DO{sub 22} IMC and fcc Cu crystals in comparison with that between the equilibrium DO{sub 3} IMC and fcc Cu crystals.

  9. Atomistic to Continuum Multiscale and Multiphysics Simulation of NiTi Shape Memory Alloy

    Science.gov (United States)

    Gur, Sourav

    Shape memory alloys (SMAs) are materials that show reversible, thermo-elastic, diffusionless, displacive (solid to solid) phase transformation, due to the application of temperature and/ or stress (/strain). Among different SMAs, NiTi is a popular one. NiTi shows reversible phase transformation, the shape memory effect (SME), where irreversible deformations are recovered upon heating, and superelasticity (SE), where large strains imposed at high enough temperatures are fully recovered. Phase transformation process in NiTi SMA is a very complex process that involves the competition between developed internal strain and phonon dispersion instability. In NiTi SMA, phase transformation occurs over a wide range of temperature and/ or stress (strain) which involves, evolution of different crystalline phases (cubic austenite i.e. B2, different monoclinic variant of martensite i.e. B19', and orthorhombic B19 or BCO structures). Further, it is observed from experimental and computational studies that the evolution kinetics and growth rate of different phases in NiTi SMA vary significantly over a wide spectrum of spatio-temporal scales, especially with length scales. At nano-meter length scale, phase transformation temperatures, critical transformation stress (or strain) and phase fraction evolution change significantly with sample or simulation cell size and grain size. Even, below a critical length scale, the phase transformation process stops. All these aspects make NiTi SMA very interesting to the science and engineering research community and in this context, the present focuses on the following aspects. At first this study address the stability, evolution and growth kinetics of different phases (B2 and variants of B19'), at different length scales, starting from the atomic level and ending at the continuum macroscopic level. The effects of simulation cell size, grain size, and presence of free surface and grain boundary on the phase transformation process

  10. Sn buffered by shape memory effect of NiTi alloys as high-performance anodes for lithium ion batteries

    International Nuclear Information System (INIS)

    Hu Renzong; Zhu Min; Wang Hui; Liu Jiangwen; Liuzhang Ouyang; Zou Jin

    2012-01-01

    By applying the shape memory effect of the NiTi alloys to buffer the Sn anodes, we demonstrate a simple approach to overcome a long-standing challenge of Sn anode in the applications of Li-ion batteries – the capacity decay. By supporting the Sn anodes with NiTi shape memory alloys, the large volume change of Sn anodes due to lithiation and delithiation can be effectively accommodated, based on the stress-induced martensitic transformation and superelastic recovery of the NiTi matrix respectively, which leads to a decrease in the internal stress and closing of cracks in Sn anodes. Accordingly, stable cycleability (630 mA h g −1 after 100 cycles at 0.7C) and excellent high-rate capabilities (478 mA h g −1 at 6.7C) were attained with the NiTi/Sn/NiTi film electrode. These shape memory alloys can also combine with other high-capacity metallic anodes, such as Si, Sb, Al, and improve their cycle performance.

  11. Effect of precipitation on the shape memory effect of Ti50Ni25Cu25 melt-spun ribbon

    International Nuclear Information System (INIS)

    Tong Yunxiang; Liu Yong; Xie Zeliang; Zarinejad, Mehrdad

    2008-01-01

    The present research aims to provide accurate understanding of the relation between precipitation (volume fraction, morphology, type) and shape memory effect of Ti 50 Ni 25 Cu 25 melt-spun ribbon. Rapid thermal annealing was used to control the microstructural development while the shape memory effect of the ribbon was determined under constraint thermal cycling. The results show that the precipitation process takes the following sequence: B11 TiCu → B11 TiCu + Ti 2 (Ni, Cu) → Ti 2 (Ni, Cu) with increasing annealing temperature or duration. The shape memory effect is found to depend on both the volume fraction and the distribution of the precipitates. The former affects the shape recovery strain through reduction of the transformation volume participating the shape recovery. The latter affects the shape recovery strain through strengthening the matrix thus reducing the martensite strain which is more predominant under low constraint stresses. Precipitation strengthening, on the other hand, reduces the tendency of dislocation generation/movement, thus reducing the irreversible strain and improving shape recovery strain. This understanding provides guidelines on the optimization of the shape memory properties of the Ti 50 Ni 25 Cu 25 melt-spun ribbon via post-processing annealing

  12. Finding the energy source for self-propagating high-temperature synthesis production of NiTi shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Novák, P.; Školáková, A.; Pignol, D.; Průša, F.; Salvetr, P.; Kubatík, Tomáš František; Perriere, L.; Karlík, M.

    2016-01-01

    Roč. 181, September (2016), s. 295-300 ISSN 0254-0584 Institutional support: RVO:61389021 Keywords : NiTi * Shape memory alloys * Powder metallurgy * Microstructure Subject RIV: JG - Metallurgy Impact factor: 2.084, year: 2016 http://www.sciencedirect.com/science/article/pii/S025405841630476X

  13. On the Ni-Ion release rate from surfaces of binary NiTi shape memory alloys

    Science.gov (United States)

    Ševčíková, Jana; Bártková, Denisa; Goldbergová, Monika; Kuběnová, Monika; Čermák, Jiří; Frenzel, Jan; Weiser, Adam; Dlouhý, Antonín

    2018-01-01

    The study is focused on Ni-ion release rates from NiTi surfaces exposed in the cell culture media and human vascular endothelial cell (HUVEC) culture environments. The NiTi surface layers situated in the depth of 70 μm below a NiTi oxide scale are affected by interactions between the NiTi alloys and the bio-environments. The finding was proved with use of inductively coupled plasma mass spectrometry and electron microscopy experiments. As the exclusive factor controlling the Ni-ion release rates was not only thicknesses of the oxide scale, but also the passivation depth, which was two-fold larger. Our experimental data strongly suggested that some other factors, in addition to the Ni concentration in the oxide scale, admittedly hydrogen soaking deep below the oxide scale, must be taken into account in order to rationalize the concentrations of Ni-ions released into the bio-environments. The suggested role of hydrogen as the surface passivation agent is also in line with the fact that the Ni-ion release rates considerably decrease in NiTi samples that were annealed in controlled hydrogen atmospheres prior to bio-environmental exposures.

  14. Interactive effects of morphine and dopaminergic compounds on spatial working memory in rhesus monkeys

    Institute of Scientific and Technical Information of China (English)

    Jian-Hong Wang; Joshua Dominie Rizak; Yan-Mei Chen; Liang Li; Xin-Tian Hu; Yuan-Ye Ma

    2013-01-01

    Opiates and dopamine (DA) play key roles in learning and memory in humans and animals.Although interactions between these neurotransmitters have been found,their functional roles remain to be fully elucidated,and their dysfunction may contribute to human diseases and addiction.Here we investigated the interactions of morphine and dopaminergic neurotransmitter systems with respect to learning and memory in rhesus monkeys by using the Wisconsin General Test Apparatus (WGTA) delayed-response task.Morphine and DA agonists (SKF-38393,apomorphine and bromocriptine) or DA antagonists (SKF-83566,haloperidol and sulpiride) were co-administered to the monkeys 30 min prior to the task.We found that dose-patterned co-administration of morphine with D1 or D2 antagonists or agonists reversed the impaired spatial working memory induced by morphine or the compounds alone.For example,morphine at 0.01 mg/kg impaired spatial working memory,while morphine (0.01 mg/kg) and apomorphine (0.01 or 0.06 mg/kg) co-treatment ameliorated this effect.Our findings suggest that the interactions between morphine and dopaminergic compounds influence spatial working memory in rhesus monkeys.A better understanding of these interactive relationships may provide insights into human addiction.

  15. Vacancy dynamic 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.; Pérez-Landazábal, J. I.; Recarte, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Plazaola, F. [Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)

    2014-06-09

    Vacancies control any atomic ordering process and consequently most of the order-dependent properties of the martensitic transformation in ferromagnetic shape memory alloys. Positron annihilation spectroscopy demonstrates to be a powerful technique to study vacancies in NiMnGa alloys quenched from different temperatures and subjected to post-quench isothermal annealing treatments. Considering an effective vacancy type the temperature dependence of the vacancy concentration has been evaluated. Samples quenched from 1173 K show a vacancy concentration of 1100 ± 200 ppm. The vacancy migration and formation energies have been estimated to be 0.55 ± 0.05 eV and 0.90 ± 0.07 eV, respectively.

  16. Atomistic study on shock behaviour of NiTi shape memory alloy

    Science.gov (United States)

    Yin, Qiuyun; Wu, Xianqian; Huang, Chenguang

    2017-06-01

    The shock behaviour of NiTi shape memory alloy is investigated by using molecular dynamics simulation. The nano-pillar samples of the alloy are subjected to the impact of a piston with a velocity of 350 m/s at initial environment temperatures of 325 and 500 K. At 325 K, we observe two different pathways of the formation of BCO phase, the gradient twins, and the detwinning phenomena, strongly depending on the local stress and the deformation state. As the initial temperature increases to 500 K, the plasticity is dominated by the dislocation movements rather than the twinning at 325 K. The phase transformation and plasticity result in stress attenuation when the stress wave propagates through the nano-pillar. Furthermore, it is interesting to note that multiple stress peaks occur due to the formation of local complex atomic structures with various wave speeds, leading to the catch up and overlap of the stress waves.

  17. Characteristics of Ti-Ni-Pd shape memory alloy thin films

    International Nuclear Information System (INIS)

    Zhang Congchun; Yang Chunsheng; Ding Duifu; Qian Shiqiang; Wu Jiansheng

    2005-01-01

    Ti-Ni-Pd thin films were deposited by RF magnetron sputtering. Microstructure and phase transformation behaviors were studied by X-ray diffraction (XRD), by transmission electron microscopy and by differential scanning calorimeter (DSC). Also tensile tests and the internal friction characteristics were examined. Annealing at 750 deg. C followed by subsequent annealing at 450 deg. C resulted in relatively homogeneous microstructure and uniform martensite/austenite transformation. The results from DSC showed clearly the martensitic transformation upon heating and cooling, the transformation temperatures are 112 deg. C (M* peak) and 91 deg. C (M peak), respectively. The transformation characteristics are also found in strain-temperature curves and internal friction-temperature curves. The film had shape memory effect. The frequency had no effect on the modulus, but the internal friction decreased with increasing frequency

  18. 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.

  19. First-principles prediction of shape memory behavior and ferrimagnetism in Mn2NiSn

    International Nuclear Information System (INIS)

    Paul, Souvik; Ghosh, Subhradip

    2011-01-01

    Using first-principles density functional theory, we show that, in Mn 2 NiSn, an energy lowering phase transition from the cubic to tetragonal phase occurs which indicates a martensitic phase transition. This structural phase transition is nearly volume-conserving, implying that this alloy can exhibit shape memory behavior. The magnetic ground state is a ferrimagnetic one with antiparallel Mn spin moments. The calculated moments with different electronic structure methods in the cubic phase compare well with each other but differ from the experimental values by more than 1 μ B . The reason behind this discrepancy is explored by considering antisite disorder in our calculations, which indicates that the site ordering in this alloy can be quite complex.

  20. Toxicity assessment and selective leaching characteristics of Cu-Al-Ni shape memory alloys in biomaterials applications.

    Science.gov (United States)

    Chang, Shih-Hang; Chen, Bor-Yann; Lin, Jin-Xiang

    2016-04-06

    Cu-Al-Ni shape memory alloys (SMAs) possess two-way shape memory effects, superelasticity, and damping capacity. Nonetheless, Cu-Al-Ni SMAs remain promising candidates for use in biomedical applications, as they are more economical and machinable than other SMAs. Ensuring the biocompatibility of Cu-Al-Ni SMAs is crucial to their development for biomedical applications. Therefore, this study aimed to assess the toxicity of Cu-Al-Ni SMAs using a Probit dose-response model and augmented simplex design. In this study, the effects of Cu2+, Al3+ and Ni2+ metal ions on bacteria (Escherichia coli DH5α) using Probit dose-response analysis and augmented simplex design to assess the actual toxicity of the Cu-Al-Ni SMAs. Extraction and repetition of Escherichia coli DH5α solutions with high Cu2+ ion concentrations and 30-hour incubation demonstrated that Escherichia coli DH5α was able to alter its growth mechanisms in response to toxins. Metal ions leached from Cu-Al-Ni SMAs appeared in a multitude of compositions with varying degrees of toxicity, and those appearing close to a saddle region identified in the contour plot of the augmented simplex model were identified as candidates for elevated toxicity levels. When the Cu-13.5Al-4Ni SMA plate was immersed in Ringer's solution, the selective leaching rate of Ni2+ ions far exceeded that of Cu2+ and Al3+. The number of Cu2+, Al3+ and Ni2+ ions leached from Cu-Al-Ni SMAs increased with immersion time; however, at higher ratios, toxicity interactions among the metal ions had the effect of gradually reducing overall toxicity levels with regard to Escherichia coli DH5α. The quantities of Cu2+, Al3+ and Ni2+ ions leached from the Cu-13.5Al-4Ni SMA plate increased with immersion time, the toxicity interactions associated with these compositions reduced the actual toxicity to Escherichia coli DH5α.

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

    International Nuclear Information System (INIS)

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

    1995-01-01

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

  2. Mechanical and shape memory properties of porous Ni50.1Ti49.9 alloys manufactured by selective laser melting.

    Science.gov (United States)

    Taheri Andani, Mohsen; Saedi, Soheil; Turabi, Ali Sadi; Karamooz, M R; Haberland, Christoph; Karaca, Haluk Ersin; Elahinia, Mohammad

    2017-04-01

    Near equiatomic NiTi shape memory alloys were fabricated in dense and designed porous forms by Selective Laser Melting (SLM) and their mechanical and shape memory properties were systematically characterized. Particularly, the effects of pore morphology on their mechanical responses were investigated. Dense and porous NiTi alloys exhibited good shape memory effect with a recoverable strain of about 5% and functional stability after eight cycles of compression. The stiffness and residual plastic strain of porous NiTi were found to depend highly on the pore shape and the level of porosity. Since porous NiTi structures have lower elastic modulus and density than dense NiTi with still good shape memory properties, they are promising materials for lightweight structures, energy absorbers, and biomedical implants. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. 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.

  4. Loading Path and Control Mode Effects During Thermomechanical Cycling of Polycrystalline Shape Memory NiTi

    Science.gov (United States)

    Nicholson, D. E.; Benafan, O.; Padula, S. A.; Clausen, B.; Vaidyanathan, R.

    2018-01-01

    Loading path dependencies and control mode effects in polycrystalline shape memory NiTi were investigated using in situ neutron and synchrotron X-ray diffraction performed during mechanical cycling and thermal cycling at constant strain. Strain-controlled, isothermal, reverse loading (to ± 4%) and stress-controlled, isothermal, cyclic loading (to ± 400 MPa for up to ten cycles) at room temperature demonstrated that the preferred martensite variants selected correlated directly with the macroscopic uniaxial strain and did not correlate with the compressive or tensile state of stress. During cyclic loading (up to ten cycles), no significant cycle-to-cycle evolution of the variant microstructure corresponding to a given strain was observed, despite changes in the slope of the stress-strain response with each cycle. Additionally, thermal cycling (to above and below the phase transformation) under constant strain (up to 2% tensile strain) showed that the martensite variant microstructure correlated directly with strain and did not evolve following thermal cycling, despite relaxation of stress in both martensite and austenite phases. Results are presented in the context of variant reorientation and detwinning processes in martensitic NiTi, the fundamental thermoelastic nature of such processes and the ability of the variant microstructure to accommodate irreversible deformation processes.

  5. Scale up of NiTi shape memory alloy production by EBM

    Science.gov (United States)

    Otubo, J.; Rigo, O. D.; Moura Neto, C.; Kaufman, M. J.; Mei, P. R.

    2003-10-01

    The usual process to produce NiTi shape memory alloy is by vacuum induction melting (VIM) using a graphite crucible, which causes contamination of the melt with carbon. Contamination with oxygen originates from the residual oxygen inside the melting chamber. An alternative process to produce NiTi alloys is by electron beam melting (EBM) using a water-cooled copper crucible that eliminates carbon contamination, and the oxygen contamination would be minimal due to operation in a vacuum of better than 10^{-2} Pa. In a previous work, it was demonstrated that the technique is feasible for button shaped samples weighing around 30g. The present work presents the results on the scale up program that enables the production of larger samples/ingots. The results are very promising in terms of chemical composition homogeneity as well as in terms of carbon contamination, the latter being four to ten times lower than the commercially-produced VIM products, and in terms of final oxygen content which is shown to depend primarily on the starting raw materials.

  6. Fiber laser drilling of Ni46Mn27Ga27 ferromagnetic shape memory alloy

    Science.gov (United States)

    Biffi, C. A.; Tuissi, A.

    2014-11-01

    The interest in ferromagnetic shape memory alloys (SMAs), such as NiMnGa, is increasing, thanks to the functional properties of these smart and functional materials. One of the most evident properties of these systems is their brittleness, which makes attractive the study of unconventional manufacturing processes, such as laser machining. In this work the interaction of laser beam, once focalized on the surface of Ni46Mn27Ga27 [at%] alloy, has been studied. The experiments were performed with a single laser pulse, using a 1 kW continuous wave fiber laser. The morphology of the laser machined surfaces was evaluated using scanning electron microscopy, coupled with energetic dispersion spectroscopy for the measurement of the chemical composition. The results showed that the high quality of the laser beam, coupled with great irradiances available, allow for blind or through holes to be machined on 1.8 mm plates with a single pulse in the order of a few ms. Holes were produced with size in the range of 200-300 μm; despite the long pulse duration, low amount of melted material is produced around the hole periphery. No significant variation of the chemical composition has been detected on the entrance surfaces while the exit ones have been characterized by the loss of Ga content, due to its melting point being significantly lower with respect to the other alloying elements.

  7. Pitting Corrosion of Ni3(Si,Ti+2Cr Intermetallic Compound at Various Chloride Concentrations

    Directory of Open Access Journals (Sweden)

    Gadang Priyotomo

    2014-05-01

    Full Text Available The pitting corrosion of Ni3(Si,Ti with 2 at% Cr containing two regions of a Ni3(Si,Ti single-phase of L12 structure and a mixture phase of of (L12 +Niss was investigated as function of chloride concentrations by using a polarization method, scanning electron microscope and energy dispersive X-Ray spectroscopy in neutral sodium chloride solutions at 293 K.  The pitting corrosion of Ni3(Si,Ti with and without the addition of aluminium and type C276 alloy were also studied under the same experimental condition for the comparison.  The pitting potential obtained for the Ni3(Si,Ti with 2 at% Cr decreased with increasing chloride concentration.  The specific pitting potentials and the pitting potentials were decreased in the order of C276 alloy > Ni3(Si,Ti > Ni3(Si,Ti + 2Cr > Ni3(Si,Ti + 4Al, which means that the pitting corrosion resistance of Ni3(Si,Ti with 2 at% Cr was higher than Ni3(Si,Ti with 4 at% Al, but lower than that of Ni3(Si,Ti.  A critical chloride concentration of Ni3(Si,Ti with 2 at% Cr was found to be higher than that of Ni3(Si,Ti with at% Al. In addition, the presence of high concentration for oxygen indicates the occurrence of pit formation.

  8. 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.

  9. Influence of Ni content on physico-chemical characteristics of Ni, Mg, Al-Hydrotalcite like compounds

    Directory of Open Access Journals (Sweden)

    Alexandre Carlos Camacho Rodrigues

    2003-12-01

    Full Text Available The physico-chemical properties of a series of Ni,Mg,Al-HTLC with Al/(Al+Mg+Ni = 0.25 and low Ni/Mg ratios were studied by means of X-ray diffraction (XRD, thermogravimetric (TGA and thermodifferential (DTA analysis, N2 physissorption and temperature programmed reduction (TPR. The as-synthesized materials were well-crystallized, with XRD patterns typical of the HTLCs in carbonate form. Upon calcination and dehydration the dehydroxilation of the layers with concurrent decomposition of carbonate anions produced mixed oxides with high surface area. XRD analysis indicated that the different nickel and aluminum oxides species are well-dispersed in a poor-crystallized MgO periclase-type phase. As observed by TPR, the different Ni species showed distinct interactions with Mg(AlO phase, which were influenced by both nickel content and calcination temperature. Regardless of the the nickel content, the reduction of nickel species was not complete as indicated by the presence of metallic dispersions.

  10. Training and two-way shape memory in NiTi alloys: influence on thermal parameters

    International Nuclear Information System (INIS)

    Lahoz, R.; Puertolas, J.A.

    2004-01-01

    The two-way shape memory effect (TWSME) was studied in a near equiatomic commercial alloy. A training procedure based on a constant load applied in the temperature range of the parent → martensite transformation was carried out on NiTi wires. The efficiency of the method was determined from deformation-temperature measurements by MTA at different training stress and number of cycles. A maximum of two shape memory strain was obtained for a stress training of 115 MPa, independently of number of training cycles. A correlation was established between the TWSME arisen and the permanent strain generated during the training. The A s and A f transitions present a positive shift and the M s and M f a negative one with increasing training stress. All the transitions temperatures decrease with the training cycling. In the trained material, the P→M and M→P temperatures and the latent heat of these conversions undergoes a strong decrease with increasing training stress, with a strong asymmetry between the forward and the reversed transitions. The changes of these thermal parameters as a function of the training parameters were studied on a thermodynamic frame

  11. An in situ neutron diffraction study of shape setting shape memory NiTi

    International Nuclear Information System (INIS)

    Benafan, O.; Padula, S.A.; Noebe, R.D.; Brown, D.W.; Clausen, B.; Vaidyanathan, R.

    2013-01-01

    A bulk polycrystalline Ni 49.9 Ti 50.1 (at.%) shape memory alloy specimen was shape set while neutron diffraction spectra were simultaneously acquired. The objective was to correlate internal stress, phase volume fraction, and texture measurements (from neutron diffraction spectra) with the macroscopic stress and shape changes (from load cell and extensometry measurements) during the shape setting procedure and subsequent shape recovery. Experimental results showed the evolution of the martensitic transformation (lattice strains, phase fractions and texture) against external constraints during both heating and cooling. Constrained heating resulted in a build-up of stresses during the martensite to austenite transformation, followed by stress relaxation due to thermal expansion, final conversion of retained martensite, and recovery processes. Constrained cooling also resulted in stress build-up arising from thermal contraction and early formation of martensite, followed by relaxation as the austenite fully transformed to martensite. Comparisons were also made between specimens pre-shape set and post-shape set with and without external constraints. The specimens displayed similar shape memory behavior consistent with the microstructure of the shape set sample, which was mostly unchanged by the shape setting process and similar to that of the as-received material

  12. Improvement of Ti-plasma coating on Ni-Ti shape memory alloy applying to implant materials and its evaluation

    International Nuclear Information System (INIS)

    Okuyama, Masaru; Endo, Jun; Take, Seisho; Itoi, Yasuhiko; Kambe, Satoshi

    2002-01-01

    Utilizing of Ni-Ti shape memory alloy for implant materials has been world-widely studied. it is, however, known that Ni-Ti alloy is easily attacked by chloride ion contained in body liquid. To prevent Ni dissolution, the authors tried to coat the alloy surface with titanium metal by means of plasma-spray coating method. The plasma coating films resulted in rather accelerating pitting corrosion because of their high porosity. Therefore, sealing of the porous films was required. In order to solve this problem and satisfy prolonged lifetime in the body, the authors tried to use the vacuum evaporation technique of titanium metal. Two types of Ti vacuum evaporation procedures were employed. The one was to cover a thin film on Ni-Ti alloy surface prior to massive Ti plasma spray coating. The other was to first coat plasma spray films on Ni-Ti alloy and then to cover them with vacuum evaporation films of Ti. Protective ability against pitting corrosion was examined by electrochemical polarization measurement in physiological solution and the coating films were characterized by microscopic and SEM observation and EPMA analysis. Vacuum evaporation thin films could not protect Ni-Ti alloy from pitting corrosion. In the case of plasma spray coating over the Ti vacuum evaporation thin film, the substrate Ni-Ti alloy could not be better protected. On the contrary, vacuum evaporation of Ti over the porous plasma spray coating layer remarkably improved corrosion protective performance

  13. Pitting Corrosion of Ni3(Si,Ti+4Al Intermetallic Compound at Various Chloride Concentrations

    Directory of Open Access Journals (Sweden)

    Gadang Priyotomo

    2014-04-01

    Full Text Available The pitting corrosion of Ni3(Si,Ti with 4 at% Al consisting of two regions of a Ni3(Si,Ti single-phase of L12 structure and two phases of L12 and fcc Niss was investigated as function of chloride concentrations by using electrochemical method, scanning electron microscope and energy dispersive X-Ray spectroscopy in neutral sodium chloride solutions at 293 K.  In addition, the pitting corrosion of Ni3(Si,Ti and  type C276 alloy were also studied under the same experimental condition for comparison.  The pitting potential obtained for the Ni3(Si,Ti with 4 at%Al decreased with increasing chloride concentration.  The specific pitting potential and pitting potential of Ni3(Si,Ti with 4at%, Ni3(Si,Ti and C276 were the lowest, the moderate and the highest, respectively, which means that the pitting corrosion resistance of Ni3(Si,Ti was higher than Ni3(Si,Ti with 4at% Al, but lower than that of C276.  A critical chloride concentration of Ni3(Si,Ti with 4at% Al was found to be lower than that of Ni3(Si,Ti.  The Pitting corrosion of Ni3(Si,Ti with 4at% Al occurred in the two phase mixture (L12 + Niss.

  14. Effect of Ta Additions on the Microstructure, Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Safaa N. Saud

    2017-01-01

    Full Text Available The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shape memory alloys was investigated in this paper. The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with the modified prealloyed Cu-Al-Ni-2.0 wt.% Ta. The phase transformation temperatures were shifted towards the highest values after Ta was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with the maximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0 wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery, and when the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Ta implied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showed that the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion current densities, higher corrosion potential, and formation of stable passive film.

  15. Effect of Ta Additions on the Microstructure, Damping, and Shape Memory Behaviour of Prealloyed Cu-Al-Ni Shape Memory Alloys.

    Science.gov (United States)

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

    2017-01-01

    The influence of Ta additions on the microstructure and properties of Cu-Al-Ni shape memory alloys was investigated in this paper. The addition of Ta significantly affects the green and porosity densities; the minimum percentage of porosity was observed with the modified prealloyed Cu-Al-Ni-2.0 wt.% Ta. The phase transformation temperatures were shifted towards the highest values after Ta was added. Based on the damping capacity results, the alloy of Cu-Al-Ni-3.0 wt.% Ta has very high internal friction with the maximum equivalent internal friction value twice as high as that of the prealloyed Cu-Al-Ni SMA. Moreover, the prealloyed Cu-Al-Ni SMAs with the addition of 2.0 wt.% Ta exhibited the highest shape recovery ratio in the first cycle (i.e., 100% recovery), and when the number of cycles is increased, this ratio tends to decrease. On the other hand, the modified alloys with 1.0 and 3.0 wt.% Ta implied a linear increment in the shape recovery ratio with increasing number of cycles. Polarization tests in NaCl solution showed that the corrosion resistance of Cu-Al-Ni-Ta SMA improved with escalating Ta concentration as shown by lower corrosion current densities, higher corrosion potential, and formation of stable passive film.

  16. First-principles calculations of two cubic fluoropervskite compounds: RbFeF3 and RbNiF3

    Science.gov (United States)

    Mubarak, A. A.; Al-Omari, Saleh

    2015-05-01

    We present first-principles calculations of the structural, elastic, electronic, magnetic and optical properties for RbFeF3 and RbNiF3. The full-potential linear augmented plan wave (FP-LAPW) method within the density functional theory was utilized to perform the present calculations. We employed the generalized gradient approximation as exchange-correlation potential. It was found that the calculated analytical lattice parameters agree with previous studies. The analysis of elastic constants showed that the present compounds are elastically stable and anisotropic. Moreover, both compounds are classified as a ductile compound. The calculations of the band structure and density functional theory revealed that the RbFeF3 compound has a half-metallic behavior while the RbNiF3 compound has a semiconductor behavior with indirect (M-Γ) band gap. The ferromagnetic behavior was studied for both compounds. The optical properties were calculated for the radiation of up to 40 eV. A beneficial optics technology is predicted as revealed from the optical spectra.

  17. Effect of Substrate Roughness on Adhesion and Structural Properties of Ti-Ni Shape Memory Alloy Thin Film.

    Science.gov (United States)

    Kim, Donghwan; Lee, Hyunsuk; Bae, Joohyeon; Jeong, Hyomin; Choi, Byeongkeun; Nam, Taehyun; Noh, Jungpil

    2018-09-01

    Ti-Ni shape memory alloy (SMA) thin films are very attractive material for industrial and medical applications such as micro-actuator, micro-sensors, and stents for blood vessels. An important property besides shape memory effect in the application of SMA thin films is the adhesion between the film and the substrate. When using thin films as micro-actuators or micro-sensors in MEMS, the film must be strongly adhered to the substrate. On the other hand, when using SMA thin films in medical devices such as stents, the deposited alloy thin film must be easily separable from the substrate for efficient processing. In this study, we investigated the effect of substrate roughness on the adhesion of Ti-Ni SMA thin films, as well as the structural properties and phase-transformation behavior of the fabricated films. Ti-Ni SMA thin films were deposited onto etched glass substrates with magnetron sputtering. Radio frequency plasma was used for etching the substrate. The adhesion properties were investigated through progressive scratch test. Structural properties of the films were determined via Feld emission scanning electron microscopy, X-ray diffraction measurements (XRD) and Energy-dispersive X-ray spectroscopy analysis. Phase transformation behaviors were observed with differential scanning calorimetry and low temperature-XRD. Ti-Ni SMA thin film deposited onto rough substrate provides higher adhesive strength than smooth substrate. However the roughness of the substrate has no influence on the growth and crystallization of the Ti-Ni SMA thin films.

  18. Low-temperature synthesis of the infinite-layer compound LaNiO2 by soft-chemical techniques

    International Nuclear Information System (INIS)

    Takamatsu, Tomohisa; Kato, Masatsune; Noji, Takashi; Koike, Yoji

    2010-01-01

    Bulk samples of LaNiO 2 with the so-called infinite-layer structure have successfully been synthesized. First, polycrystalline samples of LaNiO 3 with the perovskite structure were prepared using molten KOH at a temperature of 400-450degC. Then, they were finely ground with a double stoichiometric excess of reductant CaH 2 and sealed in an evacuated Pyrex tube. The sealed ampoule was then heated at 300degC for 24 h. Powder X-ray diffraction analysis has revealed that the product obtained after removing the residual CaH 2 and the byproduct CaO is of almost single phase with tetragonal symmetry, indicating the formation of the infinite-layer compound LaNiO 2 . (author)

  19. Influence of the particle size on phase transformation temperatures of Ni-49at.%Ti shape memory alloy powders

    International Nuclear Information System (INIS)

    Anselmo, George Carlos. S.; Castro, Walman B. de; Araujo, Carlos Jose de

    2009-01-01

    It is important to control the martensitic transformation start temperature (Ms) of Ti-Ni alloys because it determines the temperature range over which the shape memory effect and superelasticity appear. Powder metallurgy (PM) is known to provide the possibility of material saving and automated fabrication of at least semi-finished products as well as net-shape components for NiTi alloys. In this study powder with different particle sizes was subjected by gas atomization. The evolution of the control the martensitic transformation start temperature (Ms) was studied by differential scanning calorimetry. The effect of the particle size of powders on the transformation temperatures behaviors was discussed. (author)

  20. Long-term superelastic cycling at nano-scale in Cu-Al-Ni shape memory alloy micropillars

    Energy Technology Data Exchange (ETDEWEB)

    San Juan, J., E-mail: jose.sanjuan@ehu.es; Gómez-Cortés, J. F. [Dpto. Física Materia Condensada, Facultad de Ciencia y Tecnología, Univ. del País Vasco UPV/EHU, Apdo. 644, 48080 Bilbao (Spain); López, G. A.; Nó, M. L. [Dpto. Física Aplicada II, Facultad de Ciencia y Tecnología, Univ. del País Vasco UPV/EHU, Apdo. 644, 48080 Bilbao (Spain); Jiao, C. [FEI, Achtseweg Noord 5, 5651 GG Eindhoven (Netherlands)

    2014-01-06

    Superelastic behavior at nano-scale has been studied along cycling in Cu-Al-Ni shape memory alloy micropillars. Arrays of square micropillars were produced by focused ion beam milling, on slides of [001] oriented Cu-Al-Ni single crystals. Superelastic behavior of micropillars, due to the stress-induced martensitic transformation, has been studied by nano-compression tests during thousand cycles, and its evolution has been followed along cycling. Each pillar has undergone more than thousand cycles without any detrimental evolution. Moreover, we demonstrate that after thousand cycles they exhibit a perfectly reproducible and completely recoverable superelastic behavior.

  1. GRAIN-REFINEMENT AND THE RELATED PHENOMENA IN QUATERNARY Cu-Al-Ni-Ti SHAPE MEMORY ALLOYS

    OpenAIRE

    Sugimoto , K.; Kamei , K.; Matsumoto , H.; Komatsu , S.; Akamatsu , K.; Sugimoto , T.

    1982-01-01

    It was reported that the addition of a small amount of titanium (0.5 - 3.99%) to a Cu-13.93%Al-3.36%Ni ternary alloy resulted in a remarkable grain-refining. The original grain-size of about 750 microns under hot-rolled and quenched conditions of the ternary alloy was reduced to that of the order of about 100 microns by addition of tiatanium. It was suggested that several technical improvements of the mechanical properties of Cu-Al-Ni shape memory alloys, such as better formability, less crac...

  2. Longitudinal recording on FePt and FePtX (X = B, Ni) intermetallic compounds

    Science.gov (United States)

    Li, Ning

    1999-11-01

    Near field recording on high coercivity FePt intermetallic compound media using a high Bsat write element was investigated. Untextured FePt media were prepared by magnetron sputtering on ZrO2 disks at a substrate temperature of 450°C, with post annealing at 450°C for 8 hrs. Both multilayer and cosputtered precursors produced the ordered tetragonal L10 phase with high coercivity between 5kOe and 12kOe. To improve readback noise decrease magnetic domain size, FePtB media were subsequently prepared by cosputtering. Over-write, roll-off, signal to noise ratio and non-linear transition shift (NLTS) ere measured by both metal in gap (MIG) and merged MR heads. FePtB media showed similar NLTS to commercial CoCrPtTa longitudinal media, but 5dB lower signal to noise ratio. By operating recording transducers in near contact, reasonable values of (>30dB) could be obtained. VSM Rotational Transverse Magnetization has been used for measuring the anisotropy field of magnetic thin films. Magnetization reversal during rotation of a 2D isotropic an applied field is discussed. The relationship between the transverse magnetization My and the applied field H was numerically solved. An excellent approximation for the transverse magnetization is found to be: My/Ms=A(1- H/Hk) 2.5, where A = 1.1434, and Hk is the anisotropy field. For curve fitting to experimental data, both A and Hk were used as fitting parameters. Comparison between a constructed torque hysteresis method and this VSM RTM method have been made theoretically and experimentally. Both results showed that VSM RTM will give better extrapolation of the anisotropy field. The torque measurement will slightly overestimate the anisotropy field. The anisotropy fields of FePt and FePtX (X = B, Ni) films were characterized using this VSM RTM technique with comparison to a CoCrTaPt disk. Anisotropy energy was derived. Hc/Hk was used as an indicator for coherent rotation of a single domain. Interactions between magnetic domains were

  3. Regularity in the formation of compounds in ternary R-Me-Sn systems, R - REM, Me - Fe, Co, Ni, Cu

    International Nuclear Information System (INIS)

    Skolozdra, R.V.; Komarovskaya, L.P.; Koretskaya, O.Eh.

    1992-01-01

    For the ternary alloy systems of (La, Y, Gd, Lu)-Fe-Sn, (Ce, Y, Gd)-Co-Sn, (Ce, Y, Gd, Lu)-Ni-Sn and (Pr, Gd, Lu)-Cu-Sn isothermal sections of phase diagrams were plotted within the range of 670 to 870 K. It was revealed that substitution of transition metal in the kFe-Co-Ni-Cu series led to changes both in a number of ternary stannides and their structural types. A tendency was observed in change of stannide numbers depending on quantity ratio of R and Me components. Crystallochemical analysis of compounds obtained showed that they could be treated as interstitial structures or lsuperstructures with respect to them. The results of magnetic properties measurements were used for explanation of structural features of ternary compounds considered

  4. Peculiarities of the intermediate valence state of Ce in CeM2Si2 (M = Fe, Co, Ni) compounds

    International Nuclear Information System (INIS)

    Koterlyn, M.; Shcherba, I.; Yasnitskii, R.; Koterlyn, G.

    2007-01-01

    The results of thermoelectric power and the electrical resistivity measurements connected with the intermediate valence (IV) of Ce are presented for the compounds CeM 2 Si 2 (M = Fe, Co, Ni) in the temperature range of 4-800 K. It is shown that CeM 2 Si 2 are Kondo-lattices with the coherence scale T coh ∼ 60-80 K and the so-called single-site Kondo temperature T K ∼ 10 3 K. On the example of CeNi 2 Si 2 we have studied the changes in the structure of density of f states (f-DOS) near the Fermi energy caused by atomic substitutions. The results of structural, transport, magnetic, and Ce L III X-ray absorption spectra measurements in the series Ce 1-x La x Ni 2 Si 2 (0 ≤ x ≤ 0.6), Ce(Ni 1-y Cu y ) 2 Si 2 (0 ≤ y ≤ 0.6) and CeNi 2 (Si 1-z Ge z ) 2 (0 ≤ z ≤ 0.5) are presented. We found that the IV state of Ce in the CeM 2 Si 2 is an evidence of possible opening a wide pseudogap Δ ∼ kT K within the f-DOS structure slightly above the Fermi energy

  5. Transformation of technogenic compounds of Ni, Cu, Zn and Pb in different soil types in model experiment

    International Nuclear Information System (INIS)

    Ladonin, D.V.; Smirnova, M.S.; Karpukhin, M.M.; Plyaskina, O.V.

    2008-01-01

    In model experiment fractional distribution of Ni, Cu, Zn and Pb in soils artificially polluted with readily and sparingly soluble compounds (nitrates and oxides respectively) of these heavy metals was investigated. It is shown that heavy metals fractional distribution may strongly vary depending on the form in which the metal deposits in the soil. Transformation of heavy metals oxides is controlled by two main factors: solubility of an oxide and characteristics of reactions between dissolution products and the soil components

  6. PRECIPITATION BEHAVIOR OF Co PHASES IN B2-ORDERED(Ni,Co)Al COMPOUND

    Institute of Scientific and Technical Information of China (English)

    W.H. Tian; A.L. Fan; M. Nemoto

    2002-01-01

    The precipitation behavior of Co phases in B2-ordered (Ni, Co)Al has been investigatedin terms of transmission electron microscopy. Fine precipitation off cc-Co occurs in(Ni, Co)Al by aging at temperature over 973K. The orientation relationship betweenthe fcc-Co precipitates and the B2-(Ni, Co)Al matrix follows the Kurdjumow-Sachs(K-S) orientation relation. But when the aging temperature is under 873K the Coprecipitates have a hcp crystal structure. The orientation relationship between thehcp-Co precipitates and the B2-(Ni, Co)Al matrix follows the Burgers orientation re-lation. (Ni, Co)Al is hardened appreciably by the fine precipitation of both the fcc-Coand hcp-Co phases. The temperature dependence of the yield strength of precipitate-containing B2-ordered (Ni, Co)Al was investigated by compression tests over the rangeof 298-1273K. The fine precipitation of Co phases enhances greatly the low and in-termediate temperature yield strength. When the deformation temperature was over873K, the strength of precipitate-containing (Ni, Co)Al is comparable to ternary dual-phase (Ni, Co)Al+Ni3Al alloy.

  7. Low-temperature heat-capacity study of the U6X (XequivalentMn, Fe, Co, Ni) compounds

    International Nuclear Information System (INIS)

    Yang, K.N.; Maple, M.B.; DeLong, L.E.; Huber, J.G.; Junod, A.

    1989-01-01

    Measurements of the superconducting- and normal-state heat capacity of U 6 X (XequivalentMn, Fe, Co, Ni) compounds have been performed over a temperature range 1 Kapprox. 6 X compounds have strong renormalizations of the free-carrier effective mass m/sup */ in the range 10m/sub e/approx. 6 X heat capacities suggest the presence of high densities of low-energy excitations of undetermined nature. The results are analyzed in terms of models appropriate to heavy-fermion liquids, and anisotropic or strong-coupled superconductors. The U 6 X compounds form a link between relatively low-m/sup */, high-transition-temperature A15 compounds and the more extreme examples of heavy-fermion superconductors such as UBe/sub 13/, UPt 3 , and CeCuSi 2 for which m/sup */∼10 2 m/sub e/. .AE

  8. Impurity induced antiferromagnetic order in Haldane gap compound SrNi2-xMgxV2O8

    International Nuclear Information System (INIS)

    Pahari, B.; Ghoshray, K.; Ghoshray, A.; Samanta, T.; Das, I.

    2007-01-01

    The effect of nonmagnetic Mg 2+ doping in SrNi 2 V 2 O 8 , a Haldane gap system with a disordered ground state, was investigated using DC magnetic susceptibility and heat capacity measurements in polycrystalline samples of SrNi 2-x Mg x V 2 O 8 with x=0.03, 0.05, 0.07, 0.1 and 0.14. The results clearly reveal that the substitution of Ni 2+ (S=1) ion by Mg 2+ (S=0) ion induces a magnetic phase transition with the ordering temperatures lying in the range 3.4-4.3K, for the samples with lowest and highest value of x. The intrachain exchange constant (J/k B ) and the Haldane gap (Δ) for all the compounds were estimated to be ∼98+/-2 and 25K, respectively, which are close to that of the undoped compound. The magnetization data further suggest that the compounds exhibit metamagnetic behavior below T N , supporting a picture of antiferromagnet with significant magnetic anisotropy and competing intrachain and interchain interactions

  9. Formation of the distributed NiSiGe nanocrystals nonvolatile memory formed by rapidly annealing in N2 and O2 ambient

    International Nuclear Information System (INIS)

    Hu, Chih-Wei; Chang, Ting-Chang; Tu, Chun-Hao; Chiang, Cheng-Neng; Lin, Chao-Cheng; Chen, Min-Chen; Chang, Chun-Yen; Sze, Simon M.; Tseng, Tseung-Yuen

    2010-01-01

    In this work, electrical characteristics of the Ge-incorporated Nickel silicide (NiSiGe) nanocrystals memory device formed by the rapidly thermal annealing in N 2 and O 2 ambient have been studied. The trapping layer was deposited by co-sputtering the NiSi 2 and Ge, simultaneously. Transmission electron microscope results indicate that the NiSiGe nanocrystals were formed obviously in both the samples. The memory devices show obvious charge-storage ability under capacitance-voltage measurement. However, it is found that the NiSiGe nanocrystals device formed by annealing in N 2 ambient has smaller memory window and better retention characteristics than in O 2 ambient. Then, related material analyses were used to confirm that the oxidized Ge elements affect the charge-storage sites and the electrical performance of the NCs memory.

  10. Energetics of intrinsic defects in NiO and the consequences for its resistive random access memory performance

    International Nuclear Information System (INIS)

    Dawson, J. A.; Guo, Y.; Robertson, J.

    2015-01-01

    Energetics for a variety of intrinsic defects in NiO are calculated using state-of-the-art ab initio hybrid density functional theory calculations. At the O-rich limit, Ni vacancies are the lowest cost defect for all Fermi energies within the gap, in agreement with the well-known p-type behaviour of NiO. However, the ability of the metal electrode in a resistive random access memory metal-oxide-metal setup to shift the oxygen chemical potential towards the O-poor limit results in unusual NiO behaviour and O vacancies dominating at lower Fermi energy levels. Calculated band diagrams show that O vacancies in NiO are positively charged at the operating Fermi energy giving it the advantage of not requiring a scavenger metal layer to maximise drift. Ni and O interstitials are generally found to be higher in energy than the respective vacancies suggesting that significant recombination of O vacancies and interstitials does not take place as proposed in some models of switching behaviour

  11. Energetics of intrinsic defects in NiO and the consequences for its resistive random access memory performance

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, J. A., E-mail: jad95@cam.ac.uk; Guo, Y.; Robertson, J. [Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom)

    2015-09-21

    Energetics for a variety of intrinsic defects in NiO are calculated using state-of-the-art ab initio hybrid density functional theory calculations. At the O-rich limit, Ni vacancies are the lowest cost defect for all Fermi energies within the gap, in agreement with the well-known p-type behaviour of NiO. However, the ability of the metal electrode in a resistive random access memory metal-oxide-metal setup to shift the oxygen chemical potential towards the O-poor limit results in unusual NiO behaviour and O vacancies dominating at lower Fermi energy levels. Calculated band diagrams show that O vacancies in NiO are positively charged at the operating Fermi energy giving it the advantage of not requiring a scavenger metal layer to maximise drift. Ni and O interstitials are generally found to be higher in energy than the respective vacancies suggesting that significant recombination of O vacancies and interstitials does not take place as proposed in some models of switching behaviour.

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

    Science.gov (United States)

    2015-08-01

    surface coating developed during the NiTi deposition or anneal that is relatively resistant to the wet etch. Fig. 2 SEMs after the NiTi wet -etch...SEMs of NiTi devices after the 600 °C anneal , wet -etch patterning of the NiTi. A 120-nm Au capping layer was also sputtered. Figure 3a shows a 200-nm...Ni50Ti50 Cantilever 2 3. Results and Discussion 3 3.1 Wet -Etch Patterning NiTi 3 3.2 Dry-Etch Release of NiTi Devices 5 3.3 Thermal Actuation of

  13. Severe plastic deformation of melt-spun shape memory Ti2NiCu and Ni2MnGa alloys

    International Nuclear Information System (INIS)

    Pushin, Vladimir G.; Korolev, Alexander V.; Kourov, Nikolai I.; Kuntsevich, Tatiana E.; Valiev, Eduard Z.; Yurchenko, Lyudmila I.; Valiev, Ruslan Z.; Gunderov, Dmitrii V.; Zhu, Yuntian T.

    2006-01-01

    This paper describes the influence of severe plastic deformation (SPD) on the structure, phase transformations, and physical properties of melt-spun Ti 2 NiCu-based and Ni 2 MnGa-based shape memory intermetallic alloys. It was found that the SPD by high pressure torsion (HPT) at room temperature can be effectively used for the synthesis of bulk nanostructured states in these initially submicro-grained or amorphized alloys obtained by melt-spinning method in the form of a ribbon. The subsequent low-temperature annealing of HPT-processed alloys leads to formation of homogeneous ultrafine nano-grained structure. This is connected with a very high degree and high homogeneity of deformation at SPD in the whole volume of deformed samples. (author)

  14. Tribological performance of near equiatomic and Ti-rich NiTi shape memory alloy thin films

    International Nuclear Information System (INIS)

    Tillmann, Wolfgang; Momeni, Soroush

    2015-01-01

    Near equiatomic and Ti-rich NiTi shape memory alloy thin films were magnetron sputtered with the same processing parameters and thickness of 3 μm. The microstructure, composition, shape memory behavior, mechanical and tribological properties of the deposited thin films were analyzed by using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), nanoindentation, ball-on-disc, scratch test, and three dimensional (3D) optical microscopy. The obtained results clearly show how the crystallization evolution and precipitation formation of these two sets of thin films can drastically influence their mechanical and tribological performances

  15. Effect of composition on the magnetic and elastic properties shape-memory Ni-Mn-Ga

    Science.gov (United States)

    Malla, Aayush; Dapino, Marcelo J.; Lograsso, Thomas A.; Schlagel, Deborah

    2003-08-01

    The growing interest in ferromagnetic shape-memory Ni-Mn-Ga for implementation in actuator applications originates from the fact that this class of materials exhibits large strains when driven by a magnetic field. Large bidirectional strains up to a theoretical 6% are produced in these materials by twin boundary motion as martensite variants rotate to align respectively parallel or perpendicular to applied magnetic fields or stresses. These strains represent a significant improvement over piezoelectric and magnetostrictive materials. In this paper, we report on experimental measurements conducted on Ni-Mn-Ga cylindrical rods subjected to uniaxial stresses and uniaxial magnetic fields which were applied collinearly along the magnetic easy axis direction of the rods. To this end, a test apparatus was developed which consists of a water-cooled solenoid actuator and a loading fixture. Despite the lack of a readily recognizable mechanism for reversible deformations, bidirectional strains as large as 4300 ppm (0.43%) were observed, or three times the saturation magnetostriction of Terfenol-D. This paper presents room-temperature data including magnetization hysteresis, strain versus field and peak strain versus stress curves collected over a range of stresses between 0-65 MPa. From the latter set of curves, blocking force values are estimated as those for which the strain is 1% of the maximum (zero-load) strain. The results illustrate the sensitivity of material behavior with respect to composition at different driving conditions and offer insight on the choice of material compositions at which maximum actuation performance is achieved.

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

    Science.gov (United States)

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

    2005-01-01

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

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

    International Nuclear Information System (INIS)

    Otubo, J.

    1995-01-01

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

  18. Application of Taguchi method to optimization of surface roughness during precise turning of NiTi shape memory alloy

    Science.gov (United States)

    Kowalczyk, M.

    2017-08-01

    This paper describes the research results of surface quality research after the NiTi shape memory alloy (Nitinol) precise turning by the tools with edges made of polycrystalline diamonds (PCD). Nitinol, a nearly equiatomic nickel-titanium shape memory alloy, has wide applications in the arms industry, military, medicine and aerospace industry, and industrial robots. Due to their specific properties NiTi alloys are known to be difficult-to-machine materials particularly by using conventional techniques. The research trials were conducted for three independent parameters (vc, f, ap) affecting the surface roughness were analyzed. The choice of parameter configurations were performed by factorial design methods using orthogonal plan type L9, with three control factors, changing on three levels, developed by G. Taguchi. S/N ratio and ANOVA analyses were performed to identify the best of cutting parameters influencing surface roughness.

  19. The Effect of Heat Treatment on the Thermo-Elastic Behavior of Ti Ni Shape Memory Alloy

    International Nuclear Information System (INIS)

    Ahmed, K.

    2008-01-01

    The Ti-Ni shape memory alloys are used in industrial, medical and biological applications because of their outstanding mechanical properties . Research work has been done to design a remote handling unit using such alloy to work in a high neutron irradiated areas .The pre-alloyed powder is supplied by Memory-Metalle GmbH with composition Ti-49.5 at % Ni. The Metal Injection Molding (MIM) technique has been used to fabricate the alloy and subsequent different heat treatments, spectroscopic and thermal analysis have been done to test the alloy performance. Regarding to this pre-alloyed powder composition, the thermo-elastic behavior is perfect. Transformation temperature in the range 27 degree C - 63 degree C has been achieved .The final sintering quality is not satisfactory. The results show that the proposed heat treatments are not able to release the generated internal stress

  20. On the widths of the hysteresis of mechanically and thermally induced martensitic transformations in Ni-Ti-based shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jaeger, Stefanie; Maass, Burkhard; Frenzel, Jan; Schmidt, Marvin; Ullrich, Johannes; Seelecke, Stefan; Schuetze, Andreas; Kastner, Oliver; Eggeler, Gunther [Bochum Univ. (Germany). Inst. fuer Werkstoffe

    2015-10-15

    It is well known that a good crystallographic compatibility between austenite and martensite in Ni-Ti-based shape memory alloys results in narrow thermal hystereses (e.g. Ball and James, Arch. Ration. Mech. Anal., 1987). The present work suggests that a good crystallographic fit is moreover associated with a small mechanical hysteresis width, observed during a forward and reverse stress-induced transformation. Furthermore, shape memory alloys with a good crystallographic fit show smaller transformation strains. The results obtained in the present study suggest that these correlations are generic and apply to binary Ni-Ti (with varying Ni contents) and quaternary Ni-Ti-Cu-X (X = Cr, Fe, V) alloys. For binary Ni-Ti, it was observed that Ni-rich compositions (good lattice fit) show a lower accumulation of irreversible strains during pseudoelastic cycling.

  1. Effect of electrothermal annealing on the transformation behavior of TiNi shape memory alloy and two-way shape memory spring actuated by direct electrical current

    International Nuclear Information System (INIS)

    Wang, Z.G.; Zu, X.T.; Feng, X.D.; Zhu, S.; Deng, J.; Wang, L.M.

    2004-01-01

    In this work, the effect of electrothermal annealing on the transformation characterization of TiNi shape memory alloy and the electrothermal actuating characteristics of a two-way shape memory effect (TWSME) extension spring were investigated with direct electrical current. The results showed that with increasing direct electrical current density, the B2→R-phase transformation shifts to a lower temperature and R-phase→B19' shifts to a higher temperature in the cooling process. When annealing electrical current density reached 12.2 A/mm 2 , the R-phase disappeared and austenite transformed into martensite directly. The electrothermal annealing was an effective method of heat treatment in a selected part of shape memory alloy device. The electrothermal actuating characteristics of a TWSME spring showed that the time response and the maximum elongation greatly depended on the magnitude of the electrical current

  2. High frequency and magnetoelectrical properties of magnetoresistive memory element based on FeCoNi/TiN/FeCoNi film

    Directory of Open Access Journals (Sweden)

    Kurlyandskaya, G. V.

    2000-08-01

    Full Text Available A miniaturised memory device for information recording and readout processes have been designed on the basis of anisotropic magnetoresistive effect in Fe15Co20Ni65(160Å/ TiN(50Å/Fe15Co20Ni65(160Å three-layered film done by rf diode sputtering. Stable recording and readout processes were available for 32 rectangular element column, where each element had μm dimensions convenient to fabricate memory chip with 106 bits capacity. Rectangles of different sizes with removed corners were used in order to define the geometry of most of all stable recording and readout processes. Magnetoresistance and magnetoimpedance effects of a magnetic memory device have been comparatively analysed. We suggest that the decrease of the absolute value of the magnetoimpedance of the memory device comes from the reduction of the real part via the magnetoresistance.

    Se ha diseñado un dispositivo de memoria para la grabación y lectura de información basado en el efecto de la anisotropía magnetorresistiva de una multicapa fabricada por sputtering mediante diodo de rf. El elemento de memoria se compone de tres películas delgadas, de composición Fe15Co20Ni65(160Å/ TiN(50Å/Fe15Co20Ni65(160Å. El dispositivo permite procesos de grabación y lectura estables, y se compone de 32 elementos de memoria rectangulares por columna, donde cada elemento tiene dimensiones de μm lo que permite la fabricación de memorias integradas con capacidades del orden de 106 bits. Se han ensayado elementos de memoria rectangulares de diferentes tamaños, con las esquinas redondeadas con objeto de conseguir procesos de lectura-escritura lo más estable posible. Se han analizado comparativamente los efectos de magnetorresistencia y magnetoimpedancia de los elementos de memoria de diferentes dimensiones. Sugerimos que la disminución del valor absoluto de la magnetoimpedancia del elemento de memoria es consecuencia de la reducción de la parte real, de origen magnetorresistivo.

  3. Magnetic domains and twin microstructure of single crystal Ni-Mn-Ga exhibiting magnetic shape memory effect

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Kopecký, Vít; Fekete, Ladislav; Jurek, Karel; Kopeček, Jaromír; Straka, L.; Seiner, Hanuš

    2015-01-01

    Roč. 51, č. 11 (2015), s. 1-4, č. článku 2505304. ISSN 0018-9464 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:68378271 ; RVO:61388998 Keywords : magnetic domain * magnetic shape memory * NiMnGa Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.277, year: 2015

  4. Magnetic domains and twin microstructure of single crystal Ni-Mn-Ga exhibiting magnetic shape memory effect

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Kopecký, Vít; Fekete, Ladislav; Jurek, Karel; Kopeček, Jaromír; Straka, L.; Seiner, Hanuš

    2015-01-01

    Roč. 51, č. 11 (2015), s. 7150406 ISSN 0018-9464 R&D Projects: GA ČR GB14-36566G; GA MŠk LO1409 Grant - others:FUNBIO(XE) CZ.2.16/3.1.00/21568 Institutional support: RVO:68378271 ; RVO:61388998 Keywords : magnetic domain * magnetic shape memory * NiMnGa Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.277, year: 2015

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

    International Nuclear Information System (INIS)

    Nomura, K.

    1995-01-01

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

  6. Functional Properties of Porous Ti-48.0 at.% Ni Shape Memory Alloy Produced by Self-Propagating High-Temperature Synthesis

    Science.gov (United States)

    Resnina, Natalia; Belyaev, Sergey; Voronkov, Andrew

    2018-03-01

    The functional behavior of the porous shape memory alloy produced by self-propagating high-temperature synthesis from the Ti-48.0 at.% Ni powder mixture was studied. It was found that a large unelastic strain recovered on unloading and it was not attributed to the pseudoelasticity effect. A decrease in deformation temperatures did not influence the value of strain that recovered on unloading, while the effective modulus decreased from 1.9 to 1.44 GPa. It was found that the porous Ti-48.0 at.% Ni alloy revealed the one-way shape memory effect, where the maximum recoverable strain was 5%. The porous Ti-48.0 at.% Ni alloy demonstrated the transformation plasticity and the shape memory effects on cooling and heating under a stress. An increase in stress did not influence the shape memory effect value, which was equal to 1%. It was shown that the functional properties of the porous alloy were determined by the TiNi phase consisted of the two volumes Ti49.3Ni50.7 and Ti50Ni50 where the martensitic transformation occurred at different temperatures. The results of the study showed that the existence of the Ti49.3Ni50.7 volumes in the porous Ti-48.0 at.% Ni alloy improved the functional properties of the alloy.

  7. Computational modelling of Ti50Pt50-xMx shape memory alloys (M: Ni, Ir or Pd and x = 6.25-43.75 at.%)

    CSIR Research Space (South Africa)

    Modiba, Rosinah M

    2017-09-01

    Full Text Available The ab initio density functional theory approach was employed to study the effect of Ni, Ir or Pd addition to the TiPt shape memory alloy. The supercell approach in VASP was used to substitute Pt with 6.25, 18.75, 25.00, 31.25 and 43.75 at.% Ni, Ir...

  8. 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)

  9. A micromechanical constitutive model for anisotropic cyclic deformation of super-elastic NiTi shape memory alloy single crystals

    Science.gov (United States)

    Yu, Chao; Kang, Guozheng; Kan, Qianhua

    2015-09-01

    Based on the experimental observations on the anisotropic cyclic deformation of super-elastic NiTi shape memory alloy single crystals done by Gall and Maier (2002), a crystal plasticity based micromechanical constitutive model is constructed to describe such anisotropic cyclic deformation. To model the internal stress caused by the unmatched inelastic deformation between the austenite and martensite phases on the plastic deformation of austenite phase, 24 induced martensite variants are assumed to be ellipsoidal inclusions with anisotropic elasticity and embedded in the austenite matrix. The homogeneous stress fields in the austenite matrix and each induced martensite variant are obtained by using the Mori-Tanaka homogenization method. Two different inelastic mechanisms, i.e., martensite transformation and transformation-induced plasticity, and their interactions are considered in the proposed model. Following the assumption of instantaneous domain growth (Cherkaoui et al., 1998), the Helmholtz free energy of a representative volume element of a NiTi shape memory single crystal is established and the thermodynamic driving forces of the internal variables are obtained from the dissipative inequalities. The capability of the proposed model to describe the anisotropic cyclic deformation of super-elastic NiTi single crystals is first verified by comparing the predicted results with the experimental ones. It is concluded that the proposed model can capture the main quantitative features observed in the experiments. And then, the proposed model is further used to predict the uniaxial and multiaxial transformation ratchetting of a NiTi single crystal.

  10. The effect of the melting spinning cooling rate on transformation temperatures in ribbons Ti-Ni-Cu shape memory

    International Nuclear Information System (INIS)

    Ramos, A.P.; Castro, W.B.; Anselmo, G.C. dos S.

    2014-01-01

    Ti-Ni-Cu alloys have been attracting attention by their high performance of shape memory effect and decrease of thermal and stress hysteresis in comparison with Ti-Ni binary alloys. 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 Ti-37,8Cu-18,7Ni alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change of the velocity of cooling wheel from 21 to 63 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on austenitic and martensitic transformations behaviors is discussed. (author)

  11. First stage of the structural evolution of austenite in Cu-Al-Ni shape memory alloys

    International Nuclear Information System (INIS)

    Pelosin, V.; Gerland, M.; Riviere, A.

    2001-01-01

    Two shape memory Cu-Al-Ni alloys, a polycrystal and a single crystal, exhibiting a martensitic transformation close to 130 C (in the as-quenched state) have been studied. Specimens have been quenched after heat treatment at 850 C. The structural evolutions of the high temperature phase (austenite) have been studied for thermal treatments performed below 200 C. Investigations have been carried out using electrical resistivity measurements, TEM (transmission electron microscopy) observations and X-ray diffraction analysis. The main structural modifications are observed in the polycrystalline alloy and concern first, the reordering process of the austenite structure (B2→L2 1 ), and second, the precipitation of the (Cu 9 Al 4 ) γ 2 phase. In the single crystal alloy, the evolutions are very slight and localized on the structural defects. Particular attention is paid to the role of the quenched-in vacancy elimination on the observed mechanisms. In addition, the incidence of the structural evolution on the transformation temperatures is also discussed. (orig.)

  12. The specific heat of Cu-Al-Ni shape memory alloys

    International Nuclear Information System (INIS)

    Ruiz-Larrea, I.; Lopez-Echarri, A.; Bocanegra, E.H.; No, M.L.; San Juan, J.M.

    2006-01-01

    The specific heat of Cu 81.8 Al 13.7 Ni 4.5 (AK10) shape memory alloy has been studied by means of conventional DSC and adiabatic calorimetry techniques. The transformation temperatures and the shape of the calorimetric curves obtained by adiabatic calorimetry do not show any noticeable dependence on the temperature measurement rates, contrarily to what is observed by other calorimetric techniques. The dynamical character of the various experimental methods together with the influence of the latent heat associated to the first order character of these phase transitions are discussed. The specific heat of AK10 has been measured from 50 to 350 K which covers the phase transformation temperature range. The forward and reverse martensitic transformation peaks were found at 299.5 and 304.6 K, showing a thermal hysteresis of 5.1 deg. C. The C p accuracy can be estimated in 0.1% of C p and permits a reliable assignment of the following values to the phase transition thermodynamic functions: ΔH = 7.4 ± 0.2 J/g and ΔS = 0.025 ± 0.001 J/gK

  13. Development of Miniature Stewart Platform Using TiNiCu Shape-Memory-Alloy Actuators

    Directory of Open Access Journals (Sweden)

    Alaa AbuZaiter

    2015-01-01

    Full Text Available A Stewart platform is a parallel manipulator robot that is able to perform three linear movements, lateral, longitudinal, and vertical, and three rotations, pitch, yaw, and roll. This paper reports a 30 mm × 30 mm × 34 mm miniscale Stewart platform using TiNiCu shape-memory-alloy (SMA actuators. The proposed Stewart platform possesses various advantages, such as large actuation force and high robustness with a simple mechanical structure. This Stewart platform uses four SMA actuators and four bias springs and performs a linear z-axis movement and tilting motions. The SMA actuators are activated by passing a current through the SMA wires using a heating circuit that generates a pulse width modulation (PWM signal. This signal is varied to control the level of the displacement and tilting angle of the platform. The tilting direction depends on the SMA actuator that is activated, while all four SMA actuators are activated to achieve the linear z-axis movement. Each SMA actuator exerts a maximum force of 0.6 N at PWM duty cycle of 100%. The fabricated miniature Stewart platform yields a full actuation of 12 mm in the z-axis at 55°C, with a maximum tilting angle of 30° in 4 s.

  14. Transformation-Induced Relaxation and Stress Recovery of TiNi Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Kohei Takeda

    2014-03-01

    Full Text Available The transformation-induced stress relaxation and stress recovery of TiNi shape memory alloy (SMA in stress-controlled subloop loading were investigated based on the local variation in temperature and transformation band on the surface of the tape in the tension test. The results obtained are summarized as follows. (1 In the loading process, temperature increases due to the exothermic martensitic transformation (MT until the holding strain and thereafter temperature decreases while holding the strain constant, resulting in stress relaxation due to the MT; (2 In the unloading process, temperature decreases due to the endothermic reverse transformation until the holding strain and thereafter temperature increases while holding the strain constant, resulting in stress recovery due to the reverse transformation; (3 Stress varies markedly in the initial stage followed by gradual change while holding the strain constant; (4 If the stress rate is high until the holding strain in the loading and unloading processes, both stress relaxation and stress recovery are large; (5 It is important to take into account this behavior in the design of SMA elements, since the force of SMA elements varies even if the atmospheric temperature is kept constant.

  15. Atomic site occupancies and magnetic properties of Ni-doped FeAl intermetallic compounds

    CERN Document Server

    Ko, K Y; Yoon, S

    1999-01-01

    Neutron and X-ray powder diffraction revealed FeAl sub 1 sub - sub x Ni sub x alloys to have the B2(CsCl) structure with a virtually constant lattice parameter of 2.91 A and with the Ni atoms preferring the Fe sites. The annealed specimens showed paramagnetism for x 0.25 whereas the rapidly solidified specimens showed superparamagnetism for x = 0.25. The magnetization increased as the Ni concentration (x) increased. The rapidly solidified specimens, in general, showed stronger magnetic properties than the annealed ones. The magnetic properties were explained in terms of the local environmental model for magnetic atoms.

  16. The martensitic transformation in Ti-rich TiNi shape memory alloys

    International Nuclear Information System (INIS)

    Lin, H.C.; Wu, S.K.; Lin, J.C.

    1994-01-01

    The martensitic (Ms) transformation temperatures and their ΔH values of Ti 51 Ni 49 and Ti 50.5 Ni 49.5 alloys are higher than those of equiatomic or Ni-rich TiNi alloys. The Ti-rich TiNi alloys exhibit good shape recovery in spite of a great deal of second phase Ti 2 Ni or Ti 4 Ni 2 O existing around B2 grain boundaries. The nearly identical transformation temperatures indicate that the absorbed oxygen in Ti-rich TiNi alloys may react with Ti 2 Ni particles, instead of the TiNi matrix, to form Ti 4 Ni 2 O. Martensite stabilization can be induced by cold rolling at room temperature. Thermal cycling can depress the transformation temperatures significantly, especially in the initial 20 cycles. The R-phase transformation can be promoted by both cold rolling and thermal cycling in Ti-rich TiNi alloys due to introduced dislocations depressing the Ms temperature. The strengthening effects of cold rolling and thermal cycling on the Ms temperature of Ti-rich TiNi alloys are found to follow the expression Ms = To - KΔσ y . The K values are affected by different strengthening processes and related to the as-annealed transformation temperatures. The higher the as-annealed Ms (or As), the larger the K value. (orig.)

  17. Hydrodeoxygenation of lignin-derived phenolic compounds to hydrocarbons over Ni/SiO2-ZrO2 catalysts.

    Science.gov (United States)

    Zhang, Xinghua; Zhang, Qi; Wang, Tiejun; Ma, Longlong; Yu, Yuxiao; Chen, Lungang

    2013-04-01

    Inexpensive non-sulfided Ni-based catalysts were evaluated for hydrodeoxygenation (HDO) using guaiacol as model compound. SiO2-ZrO2 (SZ), a complex oxide synthesized by precipitation method with different ratio of Si/Zr, was impregnated with Ni(NO3)2·6H2O and calcined at 500°C. Conversion rates and product distribution for guaiacol HDO at 200-340°C were determined. Guaiacol conversion reached the maximum at 300°C in the presence of Ni/SZ-3. When HDO reaction was carried out with real lignin-derived phenolic compounds under the optimal conditions determined for guaiacol, the total yield of hydrocarbons was 62.81%. These hydrocarbons were comprised of cyclohexane, alkyl-substituted cyclohexane and alkyl-substituted benzene. They have high octane number, would be the most desirable components for fungible liquid transportation fuel. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Reaction of intermetallic compounds of the ScT composition (T=Ag, Cu, Zn, Ni) with hydrogen

    International Nuclear Information System (INIS)

    Shilkin, S.P.; Volkova, L.S.; Tarasov, B.P.

    1995-01-01

    Reaction of intermetallic compounds of ScT composition (T=Ag, Cu, Zn, Ni), crystallized in CsCl structural type, with hydrogen at 0.2-10 MPa pressure and 293-673 K temperature is studied by chemical, x-ray phase and complex thermogravimetry analysis methods. It is shown that under such conditions hydrogen absorption by ScAg and ScCu is accompanied by the decay of their source matrices into scandium dihydride and metal silver and copper respectively. For ScZn a fine-dispersion mixture of scandium dihydride with zinc and hydride phase of a new zinc-containing intermetallic compound appears to be the finite reaction product. In case of ScNi a hydride phase of ScNiH 2.6 composition is produced, which is crystallized in a rhombic syngony with the lattice periods: a=0.5281±0.0007, b=0.7393±0.0009 and c=0.3327±0.0004 nm. 9 refs.; 2 tabs

  19. High quality vacuum induction melting of small quantities of NiTi shape memory alloys in graphite crucibles

    International Nuclear Information System (INIS)

    Frenzel, J.; Zhang, Z.; Neuking, K.; Eggeler, G.

    2004-01-01

    Binary NiTi based shape memory alloys can be produced starting from the pure elements (Ni-pellets, Ti-rods) by using vacuum induction melting (VIM). VIM ingot metallurgy is known to produce materials with a good chemical homogeneity; it, moreover, is cheaper than vacuum arc melting (VAM) when small quantities of laboratory materials are needed. In a VIM procedure, graphite crucibles are attractive because they have appropriate electrical properties. For NiTi melting, graphite crucibles are interesting because they are reasonably priced and they show a good resistance against thermal cracking. On the other hand, it is well known that melting of Ti alloys in graphite crucibles is associated with a vigorous interface reaction. And the carbon concentration of NiTi alloys needs to be kept below a certain minimum in order to assure that the functional properties of the alloys meet the required targets. Therefore, it is important to minimize the carbon pick up of the melt. The present work presents experimental results and discusses thermodynamic and kinetic aspects of the reaction of NiTi melts with graphite crucibles; a method is suggested to keep the carbon dissolution into the melt at a minimum

  20. Magnetic properties of intermetallic compounds La(Ni,Co,Cu)3

    Science.gov (United States)

    Tazuke, Y.; Tanikawa, H.; Okano, A.; Miyaji, T.

    2006-09-01

    LaNi3 exhibited a metallic antiferromagnetic property with T N = 30 K. La(Ni1-x Cox )3 with x = 0.01, 0.03 and 0.05 exhibited ferromagnetic properties, T C increasing linearly with increasing x . La(Ni1-2z Coz Cuz )3 with z = 0.015 exhibited a ferromagnetic property with a small T C. A La(Ni1-y Cuy )3 sample with y = 0.01 exhibited a Pauli-paramagnetic property; those with y = 0.02, 0.03 and 0.04 exhibited gradual metamagnetic behavior and that with y = 0.05 exhibited a ferromagnetic property. The gradual metamagnetic M -H variations are numerically simulated by using Landau-type free energies. The results suggest that the gradual metamagnetic behavior occurs from an antiferromagnetic state to a ferromagnetic one.

  1. Structural characterization of half-metallic Heusler compound NiMnSb

    Energy Technology Data Exchange (ETDEWEB)

    Nowicki, L. E-mail: lech.nowicki@fuw.edu.pl; Abdul-Kader, A.M.; Bach, P.; Schmidt, G.; Molenkamp, L.W.; Turos, A.; Karczewski, G

    2004-06-01

    High resolution X-ray diffraction (HRXRD) and Rutherford backscattering/channeling (RBS/c) techniques were used to characterize layers of NiMnSb grown by molecular beam epitaxy (MBE) on InP with a In{sub x}Ga{sub 1-x}As buffer. Angular scans in the channeling mode reveal that the crystal structure of NiMnSb is tetragonally deformed with c/a=1.010{+-}0.002, in agreement with HRXRD data. Although HRXRD demonstrates the good quality of the pseudomorphic NiMnSb layers the channeling studies show that about 20% of atoms in the layers do not occupy lattice sites in the [0 0 1] rows of NiMnSb. The possible mechanisms responsible for the observed disorder are discussed.

  2. The High Performance Shape Memory Effect (HP-SME in Ni Rich NiTi Wires: In Situ X-Ray Diffraction on Thermal Cycling

    Directory of Open Access Journals (Sweden)

    Coduri Mauro

    2015-01-01

    Full Text Available A novel approach for using Shape Memory Alloys (SMA was recently proposed and named highperformance shape memory effect (HP-SME. The HP-SME exploits the thermal cycling of stress-induced martensite for producing extremely high mechanical work with a very stable functional fatigue behaviour in Ni rich NiTi alloy. The latter was found to differ significantly from the functional fatigue behaviour observed for conventional SMA. This study was undertaken in order to elucidate the microstructural modifications at the basis of this particular feature. To this purpose, the functional fatigue was coupled to in situ Synchrotron Radiation X-Ray Diffraction, by recording patterns on wires thermally cycled by Joule effect under a constant applied stress (800 MPa. The accurate analysis the line profile XRD data suggests the accumulation of defects upon functional cycling, while the fibre texture was not observed to change. The functional fatigue exhibits a very similar behaviour as the line broadening of XRD peaks, thus suggesting the accumulation of dislocations as the origin of the mechanism of the permanent deformation.

  3. Heat treatments and thermomechanical cycling influences on the R-phase in Ti-Ni shape memory alloys

    Directory of Open Access Journals (Sweden)

    Cezar Henrique Gonzalez

    2010-09-01

    Full Text Available This article studies changes observed on the R-phase thermoelastic behavior in a near-equiatomic Ti-Ni shape memory alloy. Three kinds of procedures have been performed: different treatments, thermomechanical cycling under constant loading in shape memory helical springs and thermal cycling in as-treated and trained samples. Several heat treatments were carried out to investigate evolution of the R-phase by differential scanning calorimetry (DSC. A heat treatment was chosen on which R-phase is absent. Shape memory springs were produced and submitted to a training process in an apparatus by tensioning the springs under constant loading. Thermal cycling in DSC was realized in as-treated and trained samples. Several aspects of one-step (B2→B19' and two-steps (B2→R→B19' martensitic transformations and R-phase formation and their evolution during tests were observed and discussed.

  4. H-Phase Precipitation and Martensitic Transformation in Ni-rich Ni-Ti-Hf and Ni-Ti-Zr High-Temperature Shape Memory Alloys

    Science.gov (United States)

    Evirgen, A.; Pons, J.; Karaman, I.; Santamarta, R.; Noebe, R. D.

    2018-03-01

    The distributions of H-phase precipitates in Ni50.3Ti29.7Hf20 and Ni50.3Ti29.7Zr20 alloys formed by aging treatments at 500 and 550 °C or slow furnace cooling and their effects on the thermal martensitic transformation have been investigated by TEM and calorimetry. The comparative study clearly reveals faster precipitate-coarsening kinetics in the NiTiZr alloy than in NiTiHf. For precipitates of a similar size of 10-20 nm in both alloys, the martensite plates in Ni50.3Ti29.7Zr20 have larger widths and span a higher number of precipitates compared with the Ni50.3Ti29.7Hf20 alloy. However, for large H-phase particles with hundreds of nm in length, no significant differences in the martensitic microstructures of both alloy systems have been observed. The martensitic transformation temperatures of Ni50.3Ti29.7Hf20 are 80-90 °C higher than those of Ni50.3Ti29.7Zr20 in the precipitate-free state and in the presence of large particles of hundreds on nm in length, but this difference is reduced to only 10-20 °C in samples with small H-phase precipitates. The changes in the transformation temperatures are consistent with the differences in the precipitate distributions between the two alloy systems observed by TEM.

  5. Observation of the structural, optical and magnetic properties during the transformation from hexagonal NiS nano-compounds to cubic NiO nanostructures due to thermal oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Linganiso, E.C., E-mail: elinganiso@csir.co.za [National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); DST/NRF Centre of Excellence in Strong Materials, Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3, Johannesburg, Wits 2050 (South Africa); Mwakikunga, B.W., E-mail: bmwakikunga@csir.co.za [National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 (South Africa); Coville, N.J. [DST/NRF Centre of Excellence in Strong Materials, Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag 3, Johannesburg, Wits 2050 (South Africa); Mhlanga, S.D. [Department of Applied Chemistry, University of Johannesburg, PO Box 17011, Doornfontein, 2028 Johannesburg (South Africa)

    2015-04-25

    Graphical abstract: The transition temperature of 350 °C for the formation of c-NiO from h-NiS oxidation was obtained from structural and optical property studies and by calculating the number of spins obtained from the EPR data. Vibrating sample magnetometry (VSM) shows that this pure NiS has both ferromagnetic ordering and paramagnetic domains. Further, the transition temperature of −9 °C of the pure α-NiS nano-alloys was confirmed by performing electrical measurements on the as-synthesized material. - Highlights: • Single hexagonal phase NiS obtained by microwave assisted hydrothermal synthesis. • NiS nanoalloys show both ferromagnetic and paramagnetic domains by VSM. • Structural evolution of annealed NiS and temperature dependent NiS oxidation presented. • Phase transition from NiS to NiO studied and correlated to the EPR spin population data and crystallite size. • Ferromagnetic and paramagnetic ordering observed for the raw NiS nanostructures. - Abstract: Single phase α-NiS nano-compounds with uniformly distributed hierarchical networks were synthesized by a microwave-assisted hydrothermal technique. The materials were evaluated for thermal stability under an oxidative environment and at temperatures between 150 °C and 600 °C. NiS materials showed stability at 300 °C and NiO formation was observed from 350 °C to 600 °C. The annealing effect on the crystalline size and IR absorption of the annealed samples is reported by XRD and FTIR studied. The EPR properties of the annealed materials were studied and compared to the oxidized materials. The transition temperature of 350 °C for the formation of NiO from NiS oxidation was confirmed by calculating the number of spins obtained from the EPR data. Vibrating sample magnetometry (VSM) shows that this pure NiS has both ferromagnetic ordering and paramagnetic domains. Further, the transition temperature of −9 °C of the pure α-NiS nano-compounds was confirmed by performing electrical

  6. Interplay of structural instability and lattice dynamics in Ni{sub 2}MnAl shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mehaddene, T.

    2007-02-12

    The work presented here is devoted to investigate the interplay of lattice dynamics and structural instability in Ni{sub 2}MnAl shape memory alloys. Inelastic neutron scattering is used to get more insight on the dynamic precursors of structural instability in Ni{sub 2}MnAl. Differential Scanning Calorimetry was used to characterise the martensitic transition in Ni{sub 2}MnAl alloys. Effects of composition and heat treatments have been investigated. The measured martensitic transition temperature in Ni-Mn-Al alloys depends linearly on the valence electron concentration. Two single crystals with different compositions have been succesfully grown using the Czochralski technique. Acoustic and optical phonon modes have been measured at room temperature in the high symmetry directions of the cubic B2 phase. The force constants have been fitted to the measured data using the Born-von Karman model. The character of the phonon softening measured in Ni{sub 2}MnAl corresponds to the pattern of atomic displacements of the modulations 2M, 10M, 12M and 14M observed in bulk and thin-films of Ni{sub 2}MnAl. The effect of the composition on the lattice instability has been investigated by measuring normal modes of vibration in two different crystals, Ni{sub 51}Mn{sub 18}Al{sub 31} and Ni{sub 53}Mn{sub 22}Al{sub 25}, with e/a ratios of 7.29 and 7.59 respectively. The stabilisation of a single L2{sub 1} phase in Ni{sub 2}MnAl by annealing a Ni{sub 51}Mn{sub 18}Al{sub 31} single crystal at 673 K during 45 days has been attempted. Despite of the long-time annealing, a single L2{sub 1} phase could not be stabilised because of either a slow diffusion kinetics or the establishment of an equilibrium between the L2{sub 1} and the B2 phases. Phonon measurements of the TA{sub 2}[{xi}{xi}0] branch in the annealed sample revealed a substantial effect. The wiggle, associated with the anomalous softening, is still present but the degree of softening is smaller below 673 K and changes

  7. Thermokinetic Simulation of Precipitation in NiTi Shape Memory Alloys

    Science.gov (United States)

    Cirstea, C. D.; Karadeniz-Povoden, E.; Kozeschnik, E.; Lungu, M.; Lang, P.; Balagurov, A.; Cirstea, V.

    2017-06-01

    Considering classical nucleation theory and evolution equations for the growth and composition change of precipitates, we simulate the evolution of the precipitates structure in the classical stages of nucleation, growth and coarsening using the solid-state transformation Matcalc software. The formation of Ni3Ti, Ni4Ti3 or Ni3Ti2 precipitate is the key to hardening phenomenon of the alloys, which depends on the nickel solubility in the bulk alloys. The microstructural evolution of metastable Ni4Ti3 and Ni3Ti2 precipitates in Ni-rich TiNi alloys is simulated by computational thermokinetics, based on thermodynamic and diffusion databases. The simulated precipitate phase fractions are compared with experimental data.

  8. Effects of annealing and deforming temperature on microstructure and deformation characteristics 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)

    2012-07-25

    Highlights: Black-Right-Pointing-Pointer The deformation behaviors of annealed Ti-50.8Ni-0.5V shape memory alloy (SMA) were given. Black-Right-Pointing-Pointer The effect of annealing temperature on microstructure and deformation characteristics of Ti-50.8Ni-0.5V SMA was shown. Black-Right-Pointing-Pointer The effect of deforming temperature on deformation characteristics of Ti-50.8Ni-0.5V SMA was given. - Abstract: Effects of annealing temperature T{sub an} and deforming temperature T{sub d} on microstructure and deformation characteristics of Ti-50.8Ni-0.5V (atomic fraction, %) shape memory alloy were investigated by means of optical microscopy and tensile test. With increasing T{sub an}, the microstructure of Ti-50.8Ni-0.5V alloy wire changes from fiber style to equiaxed grain, and the recrystallization temperature of the alloy is about 580 Degree-Sign C; the critical stress for stress-induced martensite {sigma}{sub M} of the alloy decreases first and then increases, and the minimum value 382 MPa is got at T{sub an} = 450 Degree-Sign C; the residual strain {epsilon}{sub R} first increases, then decreases, and then increases, and its maximum value 2.5% is reached at T{sub an} = 450 Degree-Sign C. With increasing T{sub d}, a transformation from shape memory effect (SME) to superelasticity (SE) occurs in the alloy annealed at different temperatures, and the SME {yields} SE transformation temperature was affected by T{sub an}; the {sigma}{sub M} of the alloy increases linearly; the {epsilon}{sub R} of the alloy annealed at 350-600 Degree-Sign C decreases first and then tends to constant, while that of the alloy annealed at 650 Degree-Sign C and 700 Degree-Sign C decreases first and then increases. To get an excellent SE at room temperature for Ti-50.8Ni-0.5V alloy, T{sub an} should be 500-600 Degree-Sign C.

  9. Designing a New Ni-Mn-Sn Ferromagnetic Shape Memory Alloy with Excellent Performance by Cu Addition

    Directory of Open Access Journals (Sweden)

    Kun Zhang

    2018-02-01

    Full Text Available Both magnetic-field-induced reverse martensitic transformation (MFIRMT and a high working temperature are crucial for the application of Ni-Mn-Sn magnetic shape memory alloys. Here, by first-principles calculations, we demonstrate that the substitution of Cu for Sn is effective not only in enhancing the MFIRMT but also in increasing martensitic transformation, which is advantageous for its application. Large magnetization difference (ΔM in Ni-Mn-Sn alloy is achieved by Cu doping, which arises from the enhancement of magnetization of austenite due to the change of Mn-Mn interaction from anti-ferromagnetism to ferromagnetism. This directly leads to the enhancement of MFIRMT. Meanwhile, the martensitic transformation shifts to higher temperature, owing to the energy difference between the austenite L21 structure and the tetragonal martensite L10 structure increases by Cu doping. The results provide the theoretical data and the direction for developing a high temperature magnetic-field-induced shape memory alloy with large ΔM in the Ni-Mn-Sn Heusler alloy system.

  10. Influence of Structure and Microstructure on Deformation Localization and Crack Growth in NiTi Shape Memory Alloys

    Science.gov (United States)

    Paul, Partha P.; Fortman, Margaret; Paranjape, Harshad M.; Anderson, Peter M.; Stebner, Aaron P.; Brinson, L. Catherine

    2018-04-01

    Porous NiTi shape memory alloys have applications in the biomedical and aerospace fields. Recent developments in metal additive manufacturing have made fabrication of near-net-shape porous products with complicated geometries feasible. There have also been developments in tailoring site-specific microstructures in metals using additive manufacturing. Inspired by these developments, we explore two related mechanistic phenomena in a simplified representation of porous shape memory alloys. First, we computationally elucidate the connection between pore geometry, stress concentration around pores, grain orientation, and strain-band formation during tensile loading of NiTi. Using this, we present a method to engineer local crystal orientations to mitigate the stress concentrations around the pores. Second, we experimentally document the growth of cracks around pores in a cyclically loaded superelastic NiTi specimen. In the areas of stress concentration around holes, cracks are seen to grow in large grains with [1 1 0] oriented along the tensile axis. This combined work shows the potential of local microstructural engineering in reducing stress concentration and increasing resistance to propagation of cracks in porous SMAs, potentially increasing the fatigue life of porous SMA components.

  11. Heterogeneous hydrogenation of unsaturated compounds with catalyst P-2-Ni with turnover numbers up to 90,000

    Energy Technology Data Exchange (ETDEWEB)

    Strohmeier, W; Pfoehler, M; Steigerwald, H [Wuerzburg Univ. (Germany, F.R.). Inst. fuer Physikalische Chemie

    1977-12-01

    Unsaturated compounds are very rapidly hydrogenated with nickel-boride catalyst P-2-Ni without solvent under mild conditions (70-85/sup 0/C and 10 bar). Turnover numbers UZ up to 90,000 and space-time-yields of 7.440 mmol product per l and 1 mgA Nickel in one hour with a mean catalyst activity a = 124 were observed. This hydrogenation catalyst has a power, which is in the same magnitude of very active noble metal catalysts.

  12. Use of response surface methodology to evaluate the effect of metal ions (Ca2+, Ni2+, Mn2+, Cu2+) on production of antifungal compounds by Paenibacillus polymyxa.

    Science.gov (United States)

    Raza, Waseem; Hongsheng, Wu; Qirong, Shen

    2010-03-01

    The effects of four metal ions (Ca(2+), Ni(2+), Mn(2+) and Cu(2+)) were evaluated on growth and production of antifungal compounds by Paenibacillus polymyxa SQR-21 and a quadratic predictive model was developed using response surface methodology (RSM). The results revealed, Mn(2+) and Ni(2+) showed most positive synergistic interactive affect on production of antifungal compounds followed by the positive interactive synergistic affect of Cu(2+) and Ni(2+) and then Mn(2+) and Cu(2+). While the interactive effect of Ca(2+) with all other three metals inhibited the production of antifungal compounds. The Mn(2+) (P=0.0384), Ni(2+) (P=0.0004) and Cu(2+) (P=0.0117) significantly affected the production of antifungal compounds while the effect of Ca(2+) (P=0.1851) was less significant. The maximum growth (OD(600)=1.55) was obtained at 500 (0), 125 (0), 100 (-2) and 37.5 (0) microM levels and the maximum size of inhibition zone (31 mm) was measured at 400 (-1), 150 (1), 400 (1) and 25 microM (-1) levels of Ca(2+), Mn(2+), Ni(2+) and Cu(2+), respectively. The RSM model provided an easy and effective way to determine the interactive effect of metal ions on production of antifungal compounds by P. polymyxa SQR-21 so that optimum media recipes can be developed to produce maximum amounts of antifungal compounds under laboratory and commercial fermentation conditions. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

  13. Effects of 7-NI and ODQ on memory in the passive avoidance, novel object recognition, and social transmission of food preference tests in mice.

    Science.gov (United States)

    Akar, Furuzan; Mutlu, Oguz; Komsuoglu Celikyurt, Ipek; Bektas, Emine; Tanyeri, Pelin; Ulak, Guner; Erden, Faruk

    2014-03-19

    Nitric oxide (NO) is an intercellular messenger that plays a critical role in learning and memory processes. Effects of nitric oxide synthase (NOS) inhibitors and guanylate cyclase (GC) inhibitors on cognitive function remain controversial. The aim of this study was to investigate effects of an NOS inhibitor, 7-nitroindazole (7-NI), and a GC inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), on different aspects of memory in passive avoidance (PA), novel object recognition (NOR), and social transmission of food preference (STFP) tests. Male Balb-c mice were treated intraperitoneally with 7-NI (15 mg/kg), ODQ (3,10 mg/kg), L-arginine (100 mg/kg) + 7-NI (15 mg/kg), or physiological saline. ODQ (10 mg/kg) and 7-NI (15 mg/kg) significantly decreased second-day latency in PA test. 7-NI (15 mg/kg) and ODQ (10 mg/kg) significantly decreased the ratio index in the NOR test. 7-NI and ODQ (10 mg/kg) decreased cued/non-cued food eaten in STFP test. Amount of time spent in center zone significantly increased in ODQ (10 mg/kg) and 7-NI (15 mg/kg) groups in open field test, but there was no effect on total distance moved and speed of animals. ODQ (10 mg/kg) significantly increased number of entries into new compartments in exploratory activity apparatus, while 7-NI had no effect. Administration of L-arginine (100 mg/kg) before 7-NI reversed 7-NI-induced effects, supporting the role of NO in cognition. Our results confirm that inhibition of NO/cGMP/GS pathway might disturb emotional, visual, and olfactory memory in mice. Also, 7-NI and ODQ had anxiolytic effects in open field test, and ODQ also enhanced exploratory activity.

  14. The effect of a fourth element (Co, Cu, Fe, Pd) on the standard enthalpy of formation of the Heusler compound Ni{sub 2}MnSn

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Ming, E-mail: myin1@hawk.iit.edu; Nash, Philip

    2016-05-15

    The standard enthalpies of formation of quaternary Heusler compounds (X, Ni){sub 2}MnSn (X = Co, Cu, Fe, Pd) were investigated experimentally using high temperature direct reaction calorimetry. Lattice parameters of these compounds were determined using X-ray diffraction analysis. Microstructures were identified using scanning electron microscopy and energy dispersive spectroscopy. The effect of an additional X element on the standard enthalpy of formation of the Heusler compound Ni{sub 2}MnSn is discussed. - Highlights: • Enthalpies of formation of (X,Ni){sub 2}YZ (X = Co, Cu, Fe, Pd) were measured by drop calorimeters. • Magnetic contribution to enthalpy of formation plays an important role. • Introducing a fourth element could stabilize an unstable Heusler structure. • Lattice parameters do not necessarily obey the Vegard's law. • It is possible to tailor properties of Heusler compounds with enough background information.

  15. Correlation between Mechanical Behavior and Actuator-type Performance of Ni-Ti-Pd High-temperature Shape Memory Alloys

    Science.gov (United States)

    Bigelow, Glen S.; Padula, Santo A., II; Garg, Anita; Noebe, Ronald D.

    2007-01-01

    High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.

  16. Magnetic characteristics of M2FeV3O11 (M = Mg, Zn, Pb, Co, Ni) compounds

    Science.gov (United States)

    Groń, T.; Blonska-Tabero, A.; Filipek, E.; Stokłosa, Z.; Duda, H.; Sawicki, B.

    2018-02-01

    The unusual physical characteristics of the multicomponent oxide systems renewed the interest as the potential cathode materials in high-energy cells. Since the earlier magnetic characteristics were not entirely conclusive, we report the results of dc magnetic measurements including higher harmonics of ac magnetic susceptibility of the M2FeV3O11 (M = Mg, Zn, Pb, Co, Ni) compounds. Ferrimagnetic long-range and antiferromagnetic short-range interactions for all compounds under study at low temperatures as well as superparamagnetic-like behavior with the blocking temperature of 29 K and the freezing parameter of 0.013 were observed. These effects are discussed within the framework of superexchange and double exchange magnetic interactions as well as the mixed valence band of iron ions.

  17. Atomistic simulation of radiation-induced amorphization of the B2 ordered intermetallic compound NiTi

    International Nuclear Information System (INIS)

    Sabochick, M.J.

    1990-12-01

    Amorphization of the B2 intermetallic compound NiTi under electron irradiation has been investigated using molecular dynamics. The effect of irradiation was simulated using two processes: (1) Ni and Ti atoms were exchanged, resulting in chemical disorder, and (2) Frenkel pairs were introduced, leading to the formation of stable point defects and also chemical disorder upon mutual recombination of interstitials and vacancies. After ∼0.4 exchanges per atom, the first process resulted in an energy increase of approximately 0.11 eV/atom and a volume increase of 1.91%. On the other hand, after introducing ∼0.5 Frenkel pairs per atom, the second process led to smaller increases of 0.092 eV/atom in energy and 1.43% in volume. The calculated radial distribution functions (RDFs) were essentially identical to each other and to the calculated RDF of a quenched liquid. The structure factor, however, showed that long-range order was still present after atom exchanges, while the introduction of Frenkel pairs resulted in the loss of long-range order. It was concluded that point defects are necessary for amorphization to occur in NiTi, although chemical disorder alone is capable of storing enough energy to make the transition possible. 18 refs., 3 figs

  18. Synthesis and Characterization of Nanocrystalline Ni50Al50-xMox (X=0-5 Intermetallic Compound During Mechanical Alloying Process

    Directory of Open Access Journals (Sweden)

    A. Khajesarvi

    2015-07-01

    Full Text Available In the present study, nanocrystalline Ni50Al50-xMox (X = 0, 0.5, 1, 2.5, 5 intermetallic compound was produced through mechanical alloying of nickel, aluminum, and molybdenum powders. AlNi compounds with good and attractive properties such as high melting point, high strength to weight ratio and high corrosion resistance especially at high temperatures have attracted the attention of many researchers. Powders produced from milling were analyzed using scanning electron microscopy (SEM and X-ray diffractometry (XRD. The results showed that intermetallic compound of NiAl formed at different stage of milling operation. It was concluded that at first disordered solid solution of (Ni,Al was formed then it converted into ordered intermetallic compound of NiAl. With increasing the atomic percent of molybdenum, average grain size decreased from 3 to 0.5 μm. Parameter lattice and lattice strain increased with increasing the atomic percent of molybdenum, while the crystal structure became finer up to 10 nm. Also, maximum microhardness was obtained for NiAl49Mo1 alloy.

  19. Magnetic properties of intermetallic compounds La(Ni,Co,Cu)3

    International Nuclear Information System (INIS)

    Tazuke, Y.; Tanikawa, H.; Okano, A.; Miyaji, T.

    2006-01-01

    LaNi 3 exhibited a metallic antiferromagnetic property with T N =30 K. La(Ni 1-x Co x ) 3 with x=0.01, 0.03 and 0.05 exhibited ferromagnetic properties, T C increasing linearly with increasing x. La(Ni 1-2z Co z Cu z ) 3 with z=0.015 exhibited a ferromagnetic property with a small T C . A La(Ni 1-y Cu y ) 3 sample with y=0.01 exhibited a Pauli-paramagnetic property; those with y=0.02, 0.03 and 0.04 exhibited gradual metamagnetic behavior and that with y=0.05 exhibited a ferromagnetic property. The gradual metamagnetic M-H variations are numerically simulated by using Landau-type free energies. The results suggest that the gradual metamagnetic behavior occurs from an antiferromagnetic state to a ferromagnetic one. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  20. Forming and control of pores by capsule-free hot isostatic pressing in NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Yuan, B; Zhu, M; Gao, Y; Li, X; Chung, C Y

    2008-01-01

    In this study, the pore evolution process of porous NiTi shape memory alloys (SMAs) fabricated by capsule-free hot isostatic pressing (CF-HIP) was investigated by adopting different fabricating parameters. It is shown that porous NiTi SMAs with homogeneous pore distribution and nearly spherical pore shape can be prepared by CF-HIP under suitable conditions. In addition, two novel pore structures were produced, one with a sandwich-like structure, and another with controlled gradient of porosity along the radial direction, with pore size increasing from the outside towards the center of the specimen. The former was obtained by balancing the pressure in the HIP chamber and the gas pressure resulting from the gas expansion in the green sample. The latter resulted from the formation of air bubbles in the liquid phase during the sintering

  1. A Novel Ni/WOX/W Resistive Random Access Memory with Excellent Retention and Low Switching Current

    Science.gov (United States)

    Chien, Wei-Chih; Chen, Yi-Chou; Lee, Feng-Ming; Lin, Yu-Yu; Lai, Erh-Kun; Yao, Yeong-Der; Gong, Jeng; Horng, Sheng-Fu; Yeh, Chiao-Wen; Tsai, Shih-Chang; Lee, Ching-Hsiung; Huang, Yu-Kai; Chen, Chun-Fu; Kao, Hsiao-Feng; Shih, Yen-Hao; Hsieh, Kuang-Yeu; Lu, Chih-Yuan

    2011-04-01

    The behavior of WOX resistive random access memory (ReRAM) is a strong function of the top electrode material, which controls the conduction mechanism and the forming process. When using a top electrode with low work function, the current conduction is limited by space charges. On the other hand, the mechanism becomes thermionic emission for devices with a high work function top electrode. These (thermionic) devices are also found to have higher initial resistance, reduced forming current, and larger resistance window. Based on these insights and considering the compatibility to complementary metal-oxide-semiconductor (CMOS) process, we proposed to use Ni as the top electrode for high performance WOX ReRAM devices. The new Ni/WOX/W device can be switched at a low current density less than 8×105 A/cm2, with RESET/SET resistance ratio greater than 100, and extremely good data retention of more than 300 years at 85 °C.

  2. Electron irradiation effect on the reverse phase transformation temperatures in TiNi shape memory alloy thin films

    International Nuclear Information System (INIS)

    Wang, Z.G.; Zu, X.T.; Fu, Y.Q.; Zhu, S.; Wang, L.M.

    2005-01-01

    In this work, Ti-Ni shape memory alloy thin films were irradiated by 1.7 MeV electron with three types of fluences: 4 x 10 20 , 7 x 10 20 and 1 x 10 21 /m 2 . The influence of electron irradiation on the transformation behavior of the TiNi thin films were investigated by differential scanning calorimetry. The transformation temperatures A s and A f shifted to higher temperature after electron irradiation, the martensite was stabilized. The electron irradiation effect can be easily eliminated by one thermal cycle. The shifts of the transformation temperatures can be explained from the change of potential energy barrier and coherency energy between parent phase and martensite after irradiation

  3. Martensitic transformation and shape memory effect in NiTi alloy covered by chitosan/silver layer

    Directory of Open Access Journals (Sweden)

    Goryczka Tomasz

    2015-01-01

    Full Text Available The NiTi shape memory alloy was covered with chitosan/silver layer. Coatings were deposited at room temperature using combination of processing parameters such as deposition voltage and amount of silver in colloidal suspension. Structure of layers was studied by means of X-ray diffraction. Quality of the coatings was evaluated basing on observations done in scanning electron microscopy. Transformation behaviour of coated samples was studied with use of differential scanning calorimeter. The covered sample revealed presence of the reversible martensitic transformation and ability to deformation (in bending mode up to 8%. Forward martensitic transformation, in as-received NiTi alloy and in alloy after layer deposition occurred in two steps B2-R-B19’. After deformation quality of the chitosan/silver layer remained unchanged.

  4. Breakdown of Shape Memory Effect in Bent Cu-Al-Ni Nanopillars: When Twin Boundaries Become Stacking Faults.

    Science.gov (United States)

    Liu, Lifeng; Ding, Xiangdong; Sun, Jun; Li, Suzhi; Salje, Ekhard K H

    2016-01-13

    Bent Cu-Al-Ni nanopillars (diameters 90-750 nm) show a shape memory effect, SME, for diameters D > 300 nm. The SME and the associated twinning are located in a small deformed section of the nanopillar. Thick nanopillars (D > 300 nm) transform to austenite under heating, including the deformed region. Thin nanopillars (D faults in the deformed region. No SME occurs and heating converts only the undeformed regions into austenite. The defect-rich, deformed region remains in the martensite phase even after prolonged heating in the stability field of austenite. A complex mixture of twins and stacking faults was found for diameters 130 nm < D < 300 nm. The size effect of the SME in Cu-Al-Ni nanopillars consists of an approximately linear reduction of the SME between 300 and 130 nm when the SME completely vanishes for smaller diameters.

  5. The study of mechanical properties and reactive stresses in the i-Ni-Nb shape memory alloys

    International Nuclear Information System (INIS)

    Popov, N.N.; Sysoeva, T.I.; Lar'kin, V.F.; Vedernikova, I.I.; Prokoshkin, S.D.

    2007-01-01

    One investigated into the effect of the induced deformation value, rate and temperature, of the thermal treatment procedure and of the chemical composition on the mechanical properties and the development of the reactive stresses in Ti-Ni-Nb system shape memory alloys. One showed the effect of the material composition and of the deformation temperature on the mechanical features of the investigated alloys. One determined the temperature and deformation conditions ensuring the maximum level of the reactive stresses in the alloys. One revealed the dependence of the maximum reactive stress value on the austenite mechanical features, namely, on its yield limit. One chose Ti-Ni-Nb alloy compositions applicable in the pipeline thermomechanical connections [ru

  6. Rubber bulge forming of single-stage bellows of TiNi shape memory alloy using the displacement control method

    International Nuclear Information System (INIS)

    Senba, Hiromasa; Yamaji, Toru; Okita, Keisuke; Okabe, Nagatoshi; Yamauchi, Kiyoshi; Matsumoto, Kenya

    2005-01-01

    This paper deals with the bulge process for forming the single-stage bellows of TiNi shape memory alloys, which is proposed as a new type of seismic applications, and especially considering the material's special behavior. Thin walled tubes with 20% cold work, whose composition is Ti-51.0 at% Ni, were prepared. First they are appropriately heat-treated and then the rubber bulge process is introduced for the tubes under the condition of austenite phase at room temperature. Displacement control method is adapted to the process. Theoretical prediction of change in outer diameter of the tube on compression is derived, and modified taking into account the progress of the stress-induced martensite transformation on tube's surface by observing the detachment of the oxide layer of the surface. Finally theoretical relationship between compressive displacement and the outer diameter of the tube, which is the most important for the design of the bellows shape, is cleared. (author)

  7. Compound Schisandra-Ginseng-Notoginseng-Lycium Extract Ameliorates Scopolamine-Induced Learning and Memory Disorders in Mice

    OpenAIRE

    Li, Ning; Liu, Cong; Jing, Shu; Wang, Mengyang; Wang, Han; Sun, Jinghui; Wang, Chunmei; Chen, Jianguang; Li, He

    2017-01-01

    Schisandra, Ginseng, Notoginseng, and Lycium barbarum are traditional Chinese medicinal plants sharing cognitive-enhancing properties. To design a functional food to improve memory, we prepared a compound Schisandra-Ginseng-Notoginseng-Lycium (CSGNL) extract and investigated its effect on scopolamine-induced learning and memory loss in mice. To optimize the dose ratios of the four herbal extracts in CSGNL, orthogonal experiments were performed. Mice were administered CSGNL by gavage once a da...

  8. The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

    Energy Technology Data Exchange (ETDEWEB)

    Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com [Research Center for Metallurgy and Material, Indonesian Institute of Sciences, Kawasan PUSPIPTEK Gd.474, Setu, Tangerang Selatan, Banten 15314 (Indonesia); Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id [Department of Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531 (Japan)

    2015-12-29

    The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observed on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.

  9. Martensitic phase transition in Cu–14%Al–4%Ni shape memory alloys studied by Brillouin light scattering

    International Nuclear Information System (INIS)

    Graczykowski, B; Mielcarek, S; Mroz, B; Breczewski, T; No, M L; San-Juan, J

    2013-01-01

    The paper presents the influence of the martensitic phase transition on hypersonic thermally excited surface acoustic waves propagating in Cu–14%Al–4%Ni (wt%) shape memory alloy. Non-destructive and non-contact testing using Brillouin light scattering spectroscopy permitted determination of the elastic constants of austenite versus temperature. Experimental results obtained for martensite were interpreted using the proposed model of the cubic to orthorhombic martensitic phase transition based on the Landau model of a first-order phase transition. Additionally we adopted the approximation of the domain structure of martensite by a polycrystalline sample using the Voigt–Reuss–Hill procedure of averaging the elastic constants. (paper)

  10. Nonlocal superelastic model of size-dependent hardening and dissipation in single crystal Cu-Al-Ni shape memory alloys.

    Science.gov (United States)

    Qiao, Lei; Rimoli, Julian J; Chen, Ying; Schuh, Christopher A; Radovitzky, Raul

    2011-02-25

    We propose a nonlocal continuum model to describe the size-dependent superelastic effect observed in recent experiments of single crystal Cu-Al-Ni shape memory alloys. The model introduces two length scales, one in the free energy and one in the dissipation, which account for the size-dependent hardening and dissipation in the loading and unloading response of micro- and nanopillars subject to compression tests. The information provided by the model suggests that the size dependence observed in the dissipation is likely to be associated with a nonuniform evolution of the distribution of the austenitic and martensitic phases during the loading cycle. © 2011 American Physical Society

  11. Orientation dependence of shape memory and super elastic effects in Ti-30% Ni-20% Cu single crystals

    International Nuclear Information System (INIS)

    Chumlyakov, Yu.I.; Kireeva, I.V.

    1999-01-01

    Single crystals of Ti-30% Ni-20% Cu (at.%) alloy experiencing B2-B19 martensitic transformation are used to study the dependence of deforming stress σ cr , shape memory effect and super elasticity on test temperature, crystal orientation and the sign of tension/compression stresses. It is shown that experimental values of shape memory effect and super elasticity as well as their dependences on orientation and loading regime are described within the frameworks of the model taking into account lattice distortions only. The orientation dependence and axial stress asymmetry in the temperature range of stress-induced martensite formation are determined by the dependence of lattice distortion during B2-B19 martensitic transformations on the orientation and the sign of applied stresses [ru

  12. Intermetallic compounds of Ni and Ga as catalysts for the synthesis of methanol

    DEFF Research Database (Denmark)

    Sharafutdinov, Irek; Elkjær, Christian Fink; de Carvalho, Hudson Wallace Pereira

    2014-01-01

    In this work, we present a detailed study of the formation of supported intermetallic Ni–Ga catalysts for CO2 hydrogenation to methanol. The bimetallic phase is formed during a temperature-programmed reduction of the metal nitrates. By utilizing a combination of characterization techniques......, in particular in situ and ex situ X-ray diffraction, in situ X-ray absorption spectroscopy, transmission electron microscopy combined with electron energy loss spectroscopy and X-ray fluorescence, we have studied the formation of intermetallic Ni–Ga catalysts of two compositions: NiGa and Ni5Ga3. These methods...... demonstrate that the catalysts with the desired intermetallic phase and composition are formed upon reduction in hydrogen and enable us to propose a mechanism of the Ni–Ga nanoparticles formation. By studying the effect of calcination prior to catalyst reduction, we show that the reactivity depends...

  13. Laser surface remelting of a Cu-Al-Ni-Mn shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Romero da Silva, Murillo, E-mail: murilloromero_@hotmail.com [Postgraduate Program in Materials Science and Engineering, Federal University of São Carlos, Rodovia Washington Luís, km 235, São Carlos, SP 13565-905 (Brazil); Gargarella, Piter [Department of Materials Engineering, Federal University of São Carlos, Rodovia Washington Luís, km 235, São Carlos, SP 13565-905 (Brazil); Gustmann, Tobias [IFW Dresden, Institute for Complex Materials, Helmholtzstraße 20, d-01069 Dresden (Germany); Botta Filho, Walter José; Kiminami, Claudio S. [Department of Materials Engineering, Federal University of São Carlos, Rodovia Washington Luís, km 235, São Carlos, SP 13565-905 (Brazil); Eckert, Jürgen [Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, A-8700 Leoben (Austria); Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben (Austria); Pauly, Simon [IFW Dresden, Institute for Complex Materials, Helmholtzstraße 20, d-01069 Dresden (Germany); Bolfarini, Claudemiro [Department of Materials Engineering, Federal University of São Carlos, Rodovia Washington Luís, km 235, São Carlos, SP 13565-905 (Brazil)

    2016-04-20

    Cu-based shape memory alloys (SMAs) show better thermal and electrical conductivity, lower cost and are easier to process than traditional Ti-based SMAs, but they exhibit a lower ductility and lower fatigue life. These properties can be improved by decreasing the grain size and reducing microstructural segregations, which may be obtained using laser surface remelting treatments. The aim of the present work was to produce and characterize laser remelted Cu-11.85Al-3.2Ni-3Mn SMA plates. Twelve plates with the dimensions of 50×10×1.5 mm were produced by suction casting in a first step. The surface of the plates was remelted afterwards with a laser beam power of 300 W, hatching of 50% and using three different scanning speeds: 100, 300 and 500 mm/s. The plates were characterized by optical and scanning electron microscopy, X-ray diffraction, differential scanning calorimetry as well as by tensile and microhardness tests. The remelted region showed a T morphology, with average thickness of 52, 29 and 23 µm for the plates remelted with scanning speeds of 100, 300 and 500 mm/s, respectively. In the plates remelted with 100 and 300 mm/s, some pores were found around the center of the track, due to the keyhole instability. The same phase formed in the as-cast sample was obtained in the laser remelted coatings: the monoclinic β′{sub 1} martensitic phase with zig-zag morphology. However, the laser treated samples exhibit lower transformation temperatures than the as-cast sample, due to grain refinement at the surface. They also show an improvement in the mechanical properties, with an increase of up to 162 MPa in fracture stress, up to 2.2% in ductility and up to 20.9 HV in microhardness when compared with the as-cast sample, which makes the laser surface remelting a promising method for improving the mechanical properties of Cu-based SMAs.

  14. Catalytic reforming of toluene as tar model compound: effect of Ce and Ce-Mg promoter using Ni/olivine catalyst.

    Science.gov (United States)

    Zhang, Ruiqin; Wang, Huajian; Hou, Xiaoxue

    2014-02-01

    Tar produced by biomass gasification as a route of renewable energy must be removed before the gas can be used. This study was undertaken using toluene as a model tar compound for evaluating its steam reforming conversion with three Ni-based catalysts, Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. Effects of Ce and Mg promoters on the reaction activity and coke deposition were studied. Overall the performance of Ce and Mg promoted Ni/olivine catalysts is better than that of only Ce promoter and Ni/olivine alone. The experimental results indicate that Ni-Ce-Mg/olivine catalysts could improve the resistance to carbon deposition, enhance energy gases yield and resist 10ppm H2S poison at 100mLmin(-1) for up to 400min. Furthermore, the activity of catalysts was related to the steam/carbon (S/C) ratios; at S/C ratio=5, T=790°C, space velocity=782h(-1) and t=2h, the Ni-Ce-Mg/olivine system yielded 89% toluene conversion, 5.6Lh(-1) product gas rate, 62.6mol% H2 content and 10% (mol useful gas mol(-1) toluene) energy yield. Moreover, at low S/C ratio, it had higher reaction activity and better ability to prevent coking. There is a small amount of carbon deposition in the form of amorphous carbon after 7h. Various characterization techniques such as XRD, FTIR and thermogravimetric were performed to investigate the coke deposition of Ni/olivine, Ni-Ce/olivine and Ni-Ce-Mg/olivine. It is suggested that 3% Ni-1% Ce-1% Mg/olivine was the most promising catalyst due to its minimum coke amount and the lower activation energy of coke burning. Copyright © 2014. Published by Elsevier Ltd.

  15. Giant negative thermal expansion in bonded MnCoGe-based compounds with Ni2In-type hexagonal structure.

    Science.gov (United States)

    Zhao, Ying-Ying; Hu, Feng-Xia; Bao, Li-Fu; Wang, Jing; Wu, Hui; Huang, Qing-Zhen; Wu, Rong-Rong; Liu, Yao; Shen, Fei-Ran; Kuang, Hao; Zhang, Ming; Zuo, Wen-Liang; Zheng, Xin-Qi; Sun, Ji-Rong; Shen, Bao-Gen

    2015-02-11

    MnCoGe-based compounds undergo a giant negative thermal expansion (NTE) during the martensitic structural transition from Ni2In-type hexagonal to TiNiSi-type orthorhombic structure. High-resolution neutron diffraction experiments revealed that the expansion of unit cell volume can be as large as ΔV/V ∼ 3.9%. The optimized compositions with concurrent magnetic and structural transitions have been studied for magnetocaloric effect. However, these materials have not been considered as NTE materials partially due to the limited temperature window of phase transition. The as-prepared MnCoGe-based compounds are quite brittle and naturally collapse into powders. By using a few percents (3-4%) of epoxy to bond the powders, we introduced residual stress in the bonded samples and thus realized the broadening of structural transition by utilizing the specific characteristics of lattice softening enforced by the stress. As a result, giant NTE (not only the linear NTE coefficient α but also the operation-temperature window) has been achieved. For example, the average α̅ as much as -51.5 × 10(-6)/K with an operating temperature window as wide as 210 K from 122 to 332 K has been observed in a bonded MnCo0.98Cr0.02Ge compound. Moreover, in the region between 250 and 305 K near room temperature, the α value (-119 × 10(-6)/K) remains nearly independent of temperature. Such an excellent performance exceeds that of most other materials reported previously, suggesting it can potentially be used as a NTE material, particularly for compensating the materials with large positive thermal expansions.

  16. The effect of applied stress on the shape memory behavior of TiNi-based alloys with different consequences of martensitic transformations

    International Nuclear Information System (INIS)

    Meisner, L.L.; Sivokha, V.P.

    2004-01-01

    The development of plastic deformation and shape memory behavior of the Ti 49.5 Ni 50.5 , Ti 50 Ni 34 Pt 16 , Ti 50 Ni 39,25 Cu 10 Fe 0,75 alloys are studied. The alloys differ by consequences of martensitic transformations (MT). It is found that the behavior of both accumulated and returned strain components exhibit some features in the alloys under consideration. The strain-temperature diagrams of the Ti 49.5 Ni 50.5 alloy with the B2↔B19' MT are of the one-step form. There are three stages on the strain-stress curves of this alloy depending on value of the applied mechanical torque. The regularity of plastic behavior of the Ti 50 Ni 34 Pt 16 alloy with the B2↔B19 transformation is similar to that of the Ti 49.5 Ni 50.5 alloy. The strain-stress diagram has three stages. However, there is a significant difference in the shape memory behavior of this alloy. The shape-memory behavior of the Ti 50 Ni 39,25 Cu 10 Fe 0,75 alloy corresponds to the two-stage nature of its B2↔B19↔B19' MT. The deformation mechanisms for these stages have their features in contrast to those of the foregoing alloys. The strain and temperature parameters of the shape memory effect and plastic behavior of the TiNi-based alloys are also examined

  17. Transformation behavior and shape memory properties of Ti50Ni15Pd25Cu10 high temperature shape memory alloy at various aging temperatures

    International Nuclear Information System (INIS)

    Rehman, Saif ur; Khan, Mushtaq; Nusair Khan, A.; Ali, Liaqat; Zaman, Sabah; Waseem, Muhammad; Ali, Liaqat; Jaffery, Syed Husain Imran

    2014-01-01

    This research presents an insight into the effect of various aging temperatures on the microstructure, hardness, phase transformation behavior and shape memory properties of Ti 50 Ni 15 Pd 25 Cu 10 high temperature shape memory alloy. The aging temperature was varied from 350 °C to 750 °C, whereas the shape memory properties were evaluated at 100–500 MPa. It was observed that the mentioned properties were strongly dependent on the aging temperatures. Based on the results obtained from scanning electron microscopy, X-ray diffractometry, microhardness testing, differential scanning calorimetry and thermomechanical testing, the aging temperatures can be divided into three ranges. At low aging temperatures (350 °C and below), the properties of the alloy remained the same as were found for solution treated sample, however at intermediate aging temperatures (400–600 °C) the properties of the alloy were changed significantly. Due to the formation of precipitates, the hardness was increased, whereas the phase transformation temperatures and work output were decreased considerably. The recovery ratio was found to be improved for intermediate aging temperatures. At high aging temperatures (650 °C and above), the hardness was decreased and the phase transformation temperatures were increased. Phase transformation temperature at the aging temperature of 750 °C was found to be increased significantly as compared to solution treated sample

  18. Development of a self-stressing NiTiNb shape memory alloy (SMA)/fiber reinforced polymer (FRP) patch

    International Nuclear Information System (INIS)

    El-Tahan, M; Dawood, M; Song, G

    2015-01-01

    The objective of this research is to develop a self-stressing patch using a combination of shape memory alloys (SMAs) and fiber reinforced polymer (FRP) composites. Prestressed carbon FRP patches are emerging as a promising alternative to traditional methods to repair cracked steel structures and civil infrastructure. However, prestressing these patches typically requires heavy and complex fixtures, which is impractical in many applications. This paper presents a new approach in which the prestressing force is applied by restraining the shape memory effect of NiTiNb SMA wires. The wires are subsequently embedded in an FRP overlay patch. This method overcomes the practical challenges associated with conventional prestressing. This paper presents the conceptual development of the self-stressing patch with the support of experimental observations. The bond between the SMA wires and the FRP is evaluated using pull-out tests. The paper concludes with an experimental study that evaluates the patch response during activation subsequent monotonic tensile loading. The results demonstrate that the self-stressing patch with NiTiNb SMA is capable of generating a significant prestressing force with minimal tool and labor requirements. (paper)

  19. The effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2014-01-01

    Based on stress-controlled cyclic tension–unloading experiments with different peak stresses, the effect of martensite plasticity on the cyclic deformation of super-elastic NiTi shape memory alloy micro-tubes is investigated and discussed. The experimental results show that the reverse transformation from the induced martensite phase to the austenite phase is gradually restricted by the plastic deformation of the induced martensite phase caused by an applied peak stress that is sufficiently high (higher than 900 MPa), and the extent of such restriction increases with further increasing the peak stress. The residual and peak strains of super-elastic NiTi shape memory alloy accumulate progressively, i.e., transformation ratchetting occurs during the cyclic tension–unloading with peak stresses from 600 to 900 MPa, and the transformation ratchetting strain increases with the increase of the peak stress. When the peak stress is higher than 900 MPa, the peak strain becomes almost unchanged, but the residual strain accumulates and the dissipation energy per cycle decreases very quickly with the increasing number of cycles due to the restricted reverse transformation by the martensite plasticity. Furthermore, a quantitative relationship between the applied stress and the stabilized residual strain is obtained to reasonably predict the evolution of the peak strain and the residual strain. (paper)

  20. Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

    Science.gov (United States)

    Bigelow, Glen S.; Padula, Santo A.; Noebe, Ronald D.; Garg, Anita; Gaydosh, Darrell

    2010-01-01

    While NiTiPd alloys have been extensively studied for proposed use in high-temperature shape-memory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd)49.5Ti50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

  1. Effects of Hydrogen Charging on the Phase Transformation of Martensitic NiTi Shape Memory Alloy Wires

    Science.gov (United States)

    Snir, Yoav; Carl, Matthew; Ley, Nathan A.; Young, Marcus L.

    2017-12-01

    Ti-rich martensitic NiTi shape memory alloy (SMA) wires of 0.5 mm diameter were tested under hydrogen-charging conditions to reveal the effects on phase transformation. Hydrogen charging was performed by immersion testing for several durations. The SMA wires were characterized by differential scanning calorimetry (DSC), scanning electron microscopy with energy dispersive spectroscopy, and synchrotron radiation X-ray diffraction (SR-XRD) for the the as-received, polished, and hydrogen-charged conditions. The DSC revealed the phase-transformation behavior of the NiTi SMA wires. Single and triple heating/cooling cycles in the DSC show the relationship between hydrogen and temperature on the material. Five distinct peaks (peaks I-V) are observed during heating/cooling in the DSC. Peak I corresponds to the martensite-to-austenite (M → A) transformation. Peaks II, III, and IV are related to hydrogen charging. Peak II appears at about 210-230 °C, while peaks III and IV appear at about 350 and 440 °C, respectively. These higher temperature peaks, peaks II-IV, were observed for the first time for a martensitic NiTi SMA due to the large temperature range covered using the DSC. Only one peak (peak V) appears during cooling and corresponds to the austenite-to-martensite transformation peak. Ex situ and in situ SR-XRD revealed the phases and the crystallographic relationship to peaks I-V in the DSC.

  2. Rapid Obtaining of Nano-Hydroxyapatite Bioactive Films on NiTi Shape Memory Alloy by Electrodeposition Process

    Science.gov (United States)

    Lobo, A. O.; Otubo, J.; Matsushima, J. T.; Corat, E. J.

    2011-07-01

    Nano-hydroxyapatite (n-HA) crystalline films have been developed in this study by electrodeposition method on NiTi shape memory alloy (SMA). The electrodeposition of the n-HA films was carried out using 0.042 mol/L Ca(NO3)2 · 4H2O + 0.025 mol/L (NH4) · 2HPO4 electrolytes by applying a constant potential of -2.0 V for 120 min and keeping the solution temperature at 70 °C. The characterization of n-HA films is of special importance since bioactive properties related to n-HA have been directly identified with its specific composition and crystalline structure. AFM, XRD, EDX, FEG-SEM and Raman spectroscopy shows a homogeneous film, with high crystallinity, special composition, and bioactivity properties (Ca/P = 1.93) of n-HA on NiTi SMA surfaces. The n-HA coating with special structure would benefit the use of NiTi alloy in orthopedic applications.

  3. Effect of different stages of deformation on the microstructure evolution of Ti-rich NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tadayyon, Ghazal, E-mail: Ghazal.tadayyon@gmail.com [Department of Metallurgical and Materials Engineering, Faculty of Engineering, Ferdowsi University of Mashhad (Iran, Islamic Republic of); Centre for Research in Medical Devices (CURAM), National University of Ireland, Galway (Ireland); Guo, Yina, E-mail: Yina.Guo@ul.ie [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Mazinani, Mohammad, E-mail: mazinani@um.ac.ir [Department of Metallurgical and Materials Engineering, Faculty of Engineering, Ferdowsi University of Mashhad (Iran, Islamic Republic of); Zebarjad, Seyed Mojtaba, E-mail: mojtabazebarjad@shirazu.ac.ir [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Tiernan, Peter, E-mail: Peter.Tiernan@ul.ie [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Tofail, Syed A.M., E-mail: Tofail.Syed@ul.ie [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Biggs, Manus J.P., E-mail: manus.biggs@nuigalway.ie [Centre for Research in Medical Devices (CURAM), National University of Ireland, Galway (Ireland)

    2017-03-15

    The main objective of this work was to investigate the thermomechanical behavior and microstructural changes of a Ti-rich NiTi shape memory alloy (SMA). The microstructural and texture evolution of aged NiTi alloy at different degrees of deformation were elicited by transmission electron microscopy (TEM). An effort was made to correlate results obtained from the tensile test with results from microstructure studies. The undeformed sample reveals a self-accommodated morphology with straight and well defined twin boundaries. At different stages of deformation, diverse mechanisms were involved. These mechanisms include marstraining, detwinning accompanied by dislocation movement, and finally, severe plastic deformation, subdivision and amorphization of the matrix. Under increasing strains, high density lattice defects were generated and the morphology of B19’ became disordered. - Graphical abstract: The summary of microstructure changes of the martensite twins during tensile deformation in polycrystalline NiTi SMAs. - Highlights: • Initial elastic response, dislocation avalanche and deformation bands were studied. • < 011 > Type II twin accompanied by detwinned area after 2% cold work was observed. • Visible parallel fine stacking faults showed plastic flow of the material. • At higher strains, subgrains changed to recrystallized, finely amorphous structure.

  4. Study of Ni50+xMn25Ga25-x (x = 2-11) as high-temperature shape-memory alloys

    International Nuclear Information System (INIS)

    Ma Yunqing; Jiang Chengbao; Li Yan; Xu Huibin; Wang Cuiping; Liu Xingjun

    2007-01-01

    Ni 50+x Mn 25 Ga 25-x (x = 2-11) alloys were studied as high-temperature shape-memory alloys, with regard to their microstructure, martensitic transformation behavior and high-temperature shape-memory effect. Single phase of martensite with tetragonal structure was present for x p increase monotonically from 39.1 deg. C for x = 2 to 443.8 deg. C for x = 7, then remain almost constant at 440 deg. C for x ≥ 7. The shape-memory strains of the alloys decreased gradually from 6.1% for x = 4 to 2.8% for x = 8 and 0% for x = 11 under the same pre-strain. The variations of the martensitic transformation temperatures and the shape-memory effects with Ni contents correlate with changes in size factor, electron concentration and precipitation of γ phase

  5. Boron-substitution and defects in B2-type AlNi compound: Site-preference and influence on structural, thermodynamic and electronic properties

    Energy Technology Data Exchange (ETDEWEB)

    Capaz, Rodrigo B. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil); ElMassalami, M., E-mail: massalam@if.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil); Terrazos, L.A. [Centro de Educação e Saúde, Universidade Federal de Campina Grande, Cuité, PB 58175-000 (Brazil); Elhadi, M. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil); Takeya, H. [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, 305-0047 (Japan); Ghivelder, L. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, Rio de Janeiro, RJ 21941-972 (Brazil)

    2016-06-05

    Using a combination of theoretical (first-principles total-energy and electronic structure calculations) as well as experimental (structural, thermodynamics) techniques, we systematically investigated the influence of B incorporation on the structural, electronic and thermodynamic properties of a series of technologically-important B-containing AlNi matrix. Special attention was paid to calculating the energy cost of placing B at various sites within the cubic unit cell. The most energetically favorable defects were identified to be, depending on initial stoichiometry, substitutional B at Al site (B{sub Al}), Ni vacancy (V{sub Ni}), or Ni antisite (Ni{sub Al}). We show that the induced variation in the lattice parameters can be correlated with the type and concentration of the involved defects: e.g. the surge of V{sub Ni} defects leads to a stronger lattice-parameter reduction, that of Ni{sub Al} ones to a relatively weaker reduction while that of B{sub Al} defects to a much weaker influence. Both electronic band structure calculations as well as thermodynamics measurements indicate that the 3d bands of Ni are fully occupied and magnetically unpolarized and that the resulting N(E{sub F}) is very small: all studied compounds are normal conductors with no trace of superconductivity or magnetic polarization.

  6. Preparation of Ni-Ti shape memory alloy by spark plasma sintering method

    Czech Academy of Sciences Publication Activity Database

    Salvetr, P.; Kubatík, Tomáš František; Novák, P.

    2016-01-01

    Roč. 16, č. 4 (2016), s. 804-808 ISSN 1213-2489 Institutional support: RVO:61389021 Keywords : Ni-Ti alloy * Powder metallurgy * Reactive sintering * Spark plasma sintering Subject RIV: JK - Corrosion ; Surface Treatment of Materials

  7. Thin Co/Ni-based bottom pinned spin-transfer torque magnetic random access memory stacks with high annealing tolerance

    Energy Technology Data Exchange (ETDEWEB)

    Tomczak, Y., E-mail: Yoann.Tomczak@imec.be [IMEC Kapeldreef 75, B-3001 Leuven (Belgium); Department of Chemistry, KU Leuven (University of Leuven), Celestijnenlaan 200F, B-3001 Leuven (Belgium); Swerts, J.; Mertens, S.; Lin, T.; Couet, S.; Sankaran, K.; Pourtois, G.; Kim, W.; Souriau, L.; Van Elshocht, S.; Kar, G.; Furnemont, A. [IMEC Kapeldreef 75, B-3001 Leuven (Belgium); Liu, E. [Department of Chemistry, KU Leuven (University of Leuven), Celestijnenlaan 200F, B-3001 Leuven (Belgium)

    2016-01-25

    Spin-transfer torque magnetic random access memory (STT-MRAM) is considered as a replacement for next generation embedded and stand-alone memory applications. One of the main challenges in the STT-MRAM stack development is the compatibility of the stack with CMOS process flows in which thermal budgets up to 400 °C are applied. In this letter, we report on a perpendicularly magnetized MgO-based tunnel junction (p-MTJ) on a thin Co/Ni perpendicular synthetic antiferromagnetic layer with high annealing tolerance. Tunnel magneto resistance (TMR) loss after annealing occurs when the reference layer loses its perpendicular magnetic anisotropy due to reduction of the CoFeB/MgO interfacial anisotropy. A stable Co/Ni based p-MTJ stack with TMR values of 130% at resistance-area products of 9 Ω μm{sup 2} after 400 °C anneal is achieved via moment control of the Co/Ta/CoFeB reference layer. Thinning of the CoFeB polarizing layer down to 0.8 nm is the key enabler to achieve 400 °C compatibility with limited TMR loss. Thinning the Co below 0.6 nm leads to a loss of the antiferromagnetic interlayer exchange coupling strength through Ru. Insight into the thickness and moment engineering of the reference layer is displayed to obtain the best magnetic properties and high thermal stability for thin Co/Ni SAF-based STT-MRAM stacks.

  8. The effect of boron additions on irradiation-induced order changes in Ni3Al intermetallic compounds

    International Nuclear Information System (INIS)

    Njah, N.; Gilbon, D.; Dimitrov, O.

    1995-01-01

    The effects of boron additions (0.1 wt%) on the kinetics of atomic order changes in a Ni 76 Al 24 intermetallic compound, under 1 MeV electron irradiation, were investigated at temperatures of 293 K and 410 K and displacement rates of 0.09 x 10 -3 to 4.7 x 10 -3 dpa.s -1 . In these irradiation conditions, a state of residual order was obtained for long irradiation times, characterized by a steady state order parameter S∞; it corresponds to a competition between two opposite features: irradiation disordering and thermal reordering enhanced by irradiation. Boron additions did not affect the efficiency of irradiation-induced disordering: the disordering cross-section (or, equivalently, the number of replacements per displacement var-epsilon) were comparable with and without a boron addition. By contrast, the S∞ values at 293 K were much lower in the alloy containing boron. Since boron does not change the disordering rate, the large difference between the values obtained in undoped and in boron-doped alloys shows that the reordering rate is strongly reduced by the presence of boron. Thus, boron modifies the mobility of the defects responsible for the irradiation-enhanced diffusion. The data on dislocation-loop size and the reordering kinetics suggest that vacancies are trapped by boron at low temperatures and immobilized, probably by the formation of a boron-vacancy complex. The effect becomes weaker at higher displacement rates and higher temperatures, probably due to the boron-vacancy complexes becoming unstable. It is proposed that two different reordering mechanisms may be operative at 293 K, according to the presence of boron: reordering is promoted by vacancy migration in the Ni 76 Al 24 alloy, whereas in the Ni 76 Al 24 (0.1 wt%B) alloy, it is promoted by the migration of split-interstitials or/and of low-mobility vacancy-boron complexes

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

  10. Influence of Test Procedures on the Thermomechanical Properties of a 55NiTi Shape Memory Alloy

    Science.gov (United States)

    Padula, Santo A., II; Gaydosh, Darrell J.; Noebe, Ronald D.; Bigelow, Glen S.; Garg, Anita; Lagoudas, Dimitris; Karaman, Ibrahim; Atli, Kadri C.

    2008-01-01

    Over the past few decades, binary NiTi shape memory alloys have received attention due to their unique mechanical characteristics, leading to their potential use in low-temperature, solid-state actuator applications. However, prior to using these materials for such applications, the physical response of these systems to mechanical and thermal stimuli must be thoroughly understood and modeled to aid designers in developing SMA-enabled systems. Even though shape memory alloys have been around for almost five decades, very little effort has been made to standardize testing procedures. Although some standards for measuring the transformation temperatures of SMA s are available, no real standards exist for determining the various mechanical and thermomechanical properties that govern the usefulness of these unique materials. Consequently, this study involved testing a 55NiTi alloy using a variety of different test methodologies. All samples tested were taken from the same heat and batch to remove the influence of sample pedigree on the observed results. When the material was tested under constant-stress, thermal-cycle conditions, variations in the characteristic material responses were observed, depending on test methodology. The transformation strain and irreversible strain were impacted more than the transformation temperatures, which only showed an affect with regard to applied external stress. In some cases, test methodology altered the transformation strain by 0.005-0.01mm/mm, which translates into a difference in work output capability of approximately 2 J/cu cm (290 in!lbf/cu in). These results indicate the need for the development of testing standards so that meaningful data can be generated and successfully incorporated into viable models and hardware. The use of consistent testing procedures is also important when comparing results from one research organization to another. To this end, differences in the observed responses will be presented, contrasted and

  11. Characterization and modeling of the magnetic field-induced strain and work output in Ni2MnGa magnetic shape memory alloys

    International Nuclear Information System (INIS)

    Kiefer, B.; Karaca, H.E.; Lagoudas, D.C.; Karaman, I.

    2007-01-01

    This paper is concerned with the experimental characterization and the constitutive modeling of magnetic shape memory alloys (MSMA), in terms of their applicability as actuator materials. The key properties that determine the actuation characteristics are the magnetic field-induced strain (MFIS) and the blocking stress. With the goal of increasing the corresponding actuation output, a material selection strategy was followed which was aimed at obtaining a higher magnetocrystalline anisotropy energy, while keeping the detwinning stress low. This was achieved by choosing a composition in which the separation of the Curie temperature and the martensitic transformation temperatures was large, and then selecting an operating temperature just below the phase transformation temperature. In the selected Ni 51.1 Mn 24.0 Ga 24.9 composition a more than 50% increase of the actuation work output was observed, compared to corresponding data reported in the literature for other off-stoichiometric compositions of the Ni 2 MnGa intermetallic compound. The second part of the paper describes a phenomenological constitutive model that predicts the MFIS hysteresis curves observed in the first part. The model is concerned with the field-induced reorientation of martensitic variants and changes in the magnetic microstructure. Dissipative effects are captured by introducing internal state variables into the free energy function. In its most general form the contributing energy terms are the elastic strain energy, the Zeeman energy, the magnetocrystalline anisotropy energy and appropriate mixing terms. Typical loading cases are considered and the accuracy of the model predictions is evaluated by comparison with the experimental data presented in the first part of this work

  12. Biocompatibility and corrosion behavior of the shape memory NiTi alloy in the physiological environments simulated with body fluids for medical applications

    International Nuclear Information System (INIS)

    Khalil-Allafi, Jafar; Amin-Ahmadi, Behnam; Zare, Mehrnoush

    2010-01-01

    Due to unique properties of NiTi shape memory alloys such as high corrosion resistance, biocompatibility, super elasticity and shape memory behavior, NiTi shape memory alloys are suitable materials for medical applications. Although TiO 2 passive layer in these alloys can prevent releasing of nickel to the environment, high nickel content and stability of passive layer in these alloys are very debatable subjects. In this study a NiTi shape memory alloy with nominal composition of 50.7 atom% Ni was investigated by corrosion tests. Electrochemical tests were performed in two physiological environments of Ringer solution and NaCl 0.9% solution. Results indicate that the breakdown potential of the NiTi alloy in NaCl 0.9% solution is higher than that in Ringer solution. The results of Scanning Electron Microscope (SEM) reveal that low pitting corrosion occurred in Ringer solution compared with NaCl solution at potentiostatic tests. The pH value of the solutions increases after the electrochemical tests. The existence of hydride products in the X-ray diffraction analysis confirms the decrease of the concentration of hydrogen ion in solutions. Topographical evaluations show that corrosion products are nearly same in all samples. The biocompatibility tests were performed by reaction of mouse fibroblast cells (L929). The growth and development of cells for different times were measured by numbering the cells or statistics investigations. The figures of cells for different times showed natural growth of cells. The different of the cell numbers between the test specimen and control specimen was negligible; therefore it may be concluded that the NiTi shape memory alloy is not toxic in the physiological environments simulated with body fluids.

  13. Ab initio study of the compound-energy modeling of multisublattice structures: The (hP6) Ni{sub 2}In-type intermetallics of the Ni–In–Sn system

    Energy Technology Data Exchange (ETDEWEB)

    Ramos de Debiaggi, S., E-mail: susana.ramos@fain.uncoma.edu.ar [Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén (Argentina); Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energías Alternativas – CONICET-UNCo (Argentina); González Lemus, N.V. [Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires 1400, 8300 Neuquén (Argentina); Deluque Toro, C. [Grupo de Nuevos Materiales, Universidad de la Guajira, Riohacha (Colombia); Fernández Guillermet, A. [CONICET - Instituto Balseiro, Centro Atómico Bariloche, Avda. Bustillo 9500, 8400 Bariloche (Argentina)

    2015-01-15

    Highlights: • A DFT study of the compounds involved in CALPHAD modeling of the Ni–In–Sn (hP6) phase. • Several three-sublattice compounds of Ni, In, Sn and vacancies are studied ab initio. • Structural, cohesive and thermodynamic properties and the electronic DOS are reported. • Trends in calculated properties are correlated with changes in electronic structure. • A picture of the chemical bonding trends for these s-p/d type compounds is discussed. - Abstract: The thermodynamic modeling of non-stoichiometric, multisublattice intermetallic phases using the Compound-Energy Formalism (CEF) involves the determination of parameters representing the Gibbs energy (G{sub m}) of binary compounds, the so-called “end-member compounds” (EMCs), which are often metastable or hypothetical. In current CALPHAD (i.e., “Calculation of Phase Diagrams”) work, these quantities are treated as free parameters to be determined by searching for the best fit to the available information in the optimization procedure. The general purpose of this paper is to propose a theoretical approach to the study of the EMCs which makes use of density-functional-theory (DFT) ab initio calculations. The present method is applied to the EMCs involved in the CEF modeling of the non-stoichiometric (hP6) Ni{sub 2}In-structure type phase of the Ni–In and Ni–In–Sn systems using the three-sublattice models (Ni){sub 1}(Ni,Va){sub 1}(In,Ni){sub 1} and (Ni,Va){sub 1}(Ni,Va){sub 1}(In,Ni,Sn){sub 1}, respectively. By means of systematic ab initio projected augmented waves (PAW) calculations using the VASP code we study the EMCs involved in the CEF formulations of the G{sub m} for this phase in the binary and the ternary systems. Specifically, we study the twelve EMCs corresponding to the following sublattice occupations: (Ni){sub 1}(Ni){sub 1}(In){sub 1}, which is usually described as Ni:Ni:In (i.e., a compound with formula “Ni{sub 2}In”), Ni:Ni:Ni (i.e., “Ni{sub 3}”), Ni:Ni:Sn (“Ni

  14. Ab initio study of the compound-energy modeling of multisublattice structures: The (hP6) Ni2In-type intermetallics of the Ni–In–Sn system

    International Nuclear Information System (INIS)

    Ramos de Debiaggi, S.; González Lemus, N.V.; Deluque Toro, C.; Fernández Guillermet, A.

    2015-01-01

    Highlights: • A DFT study of the compounds involved in CALPHAD modeling of the Ni–In–Sn (hP6) phase. • Several three-sublattice compounds of Ni, In, Sn and vacancies are studied ab initio. • Structural, cohesive and thermodynamic properties and the electronic DOS are reported. • Trends in calculated properties are correlated with changes in electronic structure. • A picture of the chemical bonding trends for these s-p/d type compounds is discussed. - Abstract: The thermodynamic modeling of non-stoichiometric, multisublattice intermetallic phases using the Compound-Energy Formalism (CEF) involves the determination of parameters representing the Gibbs energy (G m ) of binary compounds, the so-called “end-member compounds” (EMCs), which are often metastable or hypothetical. In current CALPHAD (i.e., “Calculation of Phase Diagrams”) work, these quantities are treated as free parameters to be determined by searching for the best fit to the available information in the optimization procedure. The general purpose of this paper is to propose a theoretical approach to the study of the EMCs which makes use of density-functional-theory (DFT) ab initio calculations. The present method is applied to the EMCs involved in the CEF modeling of the non-stoichiometric (hP6) Ni 2 In-structure type phase of the Ni–In and Ni–In–Sn systems using the three-sublattice models (Ni) 1 (Ni,Va) 1 (In,Ni) 1 and (Ni,Va) 1 (Ni,Va) 1 (In,Ni,Sn) 1 , respectively. By means of systematic ab initio projected augmented waves (PAW) calculations using the VASP code we study the EMCs involved in the CEF formulations of the G m for this phase in the binary and the ternary systems. Specifically, we study the twelve EMCs corresponding to the following sublattice occupations: (Ni) 1 (Ni) 1 (In) 1 , which is usually described as Ni:Ni:In (i.e., a compound with formula “Ni 2 In”), Ni:Ni:Ni (i.e., “Ni 3 ”), Ni:Ni:Sn (“Ni 2 Sn”), Ni:Va:In (i.e., “NiIn”), Ni:Va:Ni (i

  15. Martensitic transformation and shape memory effect in Ni54.75Mn13.25Fe7Ga25 ferromagnetic shape memory alloy

    International Nuclear Information System (INIS)

    Wang, H.B.; Sui, J.H.; Liu, C.; Cai, W.

    2008-01-01

    The martensitic transformation and shape memory effect of Ni 54.75 Mn 13.25 Fe 7 Ga 25 (at.%) alloy are studied in the present paper. It is shown that tetragonal martensite with parallel bands substructure transforms to parent phase heated by electron beam. It can be clearly observed that the martensite band becomes smaller and smaller, then transforms to parent phase completely in the end. A large reversible transformation strain, about 1.5%, is obtained in this undeformed polycrystalline alloy due to martensitic transformation and its reverse transformation. This transformation strain is also increased to 1.8% by the external magnetic field. It is believed that the effect of the magnetic field on the preferential orientation of martensitic variants increases the transformation strain

  16. Acoustic wave propagation in Ni3 R (R = Mo, Nb, Ta) compounds

    Indian Academy of Sciences (India)

    tile and stable, and contains few defects in the crystal structure in comparison to other compounds. 4. Conclusions. Based on the above discussion it is worthwhile to state that. • Present method to evaluate second-order elastic constants involving many- body interaction potential for hexagonal wurtzite crystal structured ...

  17. Coordination Compounds of Co Ni , Cu , Zn , Cd and Hg with ...

    African Journals Online (AJOL)

    CLEMENT O BEWAJI

    Bipin B. Mahapatra* and Saroj Ku. Panda. **. **P.G. Department of Chemistry, G.M. (Autonomous) College, Sambalpur – 768004 (Orissa). India. Telephone ..... Ferraro, J.R: Low Frequency Vibration of Inorganic and Co-ordination Compound Plenum press, New York. USA: (1971). 10. Sacconi. L: J. Inorg. Nucl. Chem., 18 ...

  18. Lattice heat capacity in RTAl (R = Y, Lu; T = Ni, Cu, Pd) compounds

    Czech Academy of Sciences Publication Activity Database

    Daniel, P.; Javorský, P.; Prchal, J.; Šantavá, Eva; Daniš, S.

    2008-01-01

    Roč. 113, č. 1 (2008), s. 331-334 ISSN 0587-4246. [CSMAG'07. Košice, 09.07.2007-12.07.2007] Institutional research plan: CEZ:AV0Z10100520 Keywords : RTAl compounds * specific heat Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.321, year: 2008

  19. Microstructural evolution and magnetic properties of binder jet additive manufactured Ni-Mn-Ga magnetic shape memory alloy foam

    International Nuclear Information System (INIS)

    Mostafaei, Amir; Kimes, Katerina A.; Stevens, Erica L.; Toman, Jakub; Krimer, Yuval L.; Ullakko, Kari; Chmielus, Markus

    2017-01-01

    This study investigated microstructural evolution, phase transformation and magnetic behavior of additively manufactured magnetic shape memory alloy foam. Pre-alloyed angular Ni-Mn-Ga ball-milled powder was binder jet printed and sintered at 1020 °C for 4 h in both vacuum and argon atmospheres. Porosity of the manufactured foams was studied using micro-computed x-ray tomography and it was found that the relative density of the sintered parts was about 50–60%. In the printed sample that was sintered in argon, electron microscopy with elemental analysis showed no compositional gradient. X-ray diffraction indicated that 10M modulated martensite was present in the pre-alloyed powder as well as the sample sintered in argon. Differential scanning calorimetry and thermomagnetic results showed that martensitic transformation of the sample sintered in argon was at 34 °C, while barely detectable in the sample sintered in vacuum. Saturation magnetization of the printed sample sintered in argon atmosphere was around 68.4 Am"2/kg. Production of a magnetic shape memory alloy by printing would enable complex-shaped elements for demanding applications, and intentionally including porosity could allow these polycrystals to exhibit the magnetic shape memory effect. Therefore, a facile method for sintering of Ni–Mn–Ga printed parts has been presented for the first time.

  20. Single crystals of the anisotropic Kagome staircase compounds Ni3V2O8 and Co3V2O8

    OpenAIRE

    Balakrishnan, G.; Petrenko, O. A.; Lees, M. R.; Paul, D. McK.

    2004-01-01

    Compounds with a Kagome type lattice are known to exhibit magnetic frustration. Large single crystals of two compounds Ni3V2O8 and Co3V2O8, which are variants of a Kagome net lattice, have been grown successfully by the floating zone technique using an optical image furnace. The single crystals are of high quality and exhibit intriguing magnetic properties.

  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

    necessary anneal . Following this, a thin film of NiTi was blanket sputtered at 600 °C. This NiTi blanket layer was then wet -etch patterned using a...varying the sputter parameters during NiTi deposition, such as thickness, substrate temperature during deposition and anneal , and argon pressure during...6 Fig. 4 Surface texture comparison between NiTi sputtered at RT, then annealed at 600 °C, and NiTi

  2. Grain size effects on stability of nonlinear vibration with nanocrystalline NiTi shape memory alloy

    Science.gov (United States)

    Xia, Minglu; Sun, Qingping

    2017-10-01

    Grain size effects on stability of thermomechanical responses for a nonlinear torsional vibration system with nanocrystalline superelastic NiTi bar are investigated in the frequency and amplitude domains. NiTi bars with average grain size from 10 nm to 100 nm are fabricated through cold-rolling and subsequent annealing. Thermomechanical responses of the NiTi bar as a softening nonlinear damping spring in the torsional vibration system are obtained by synchronised acquisition of rotational angle and temperature under external sinusoidal excitation. It is shown that nonlinearity and damping capacity of the NiTi bar decrease as average grain size of the material is reduced below 100 nm. Therefore jump phenomena of thermomechanical responses become less significant or even vanish and the vibration system becomes more stable. The work in this paper provides a solid experimental base for manipulating the undesired jump phenomena of thermomechanical responses and stabilising the mechanical vibration system through grain refinement of NiTi SMA.

  3. Investigation of route to martensitic transition in Ni-Mn-In shape memory alloys

    Science.gov (United States)

    Nevgi, R.; Priolkar, K. R.; Righi, L.

    2018-04-01

    The temperature dependent x-ray diffraction and magnetization measurements on the off stoichiometric Ni2Mn1+xIn1-x alloys have confirmed the appearance of martensite at critical Mn concentration of x=0.35. The high temperature phase of all the alloys have cubic L21 structure with the lattice constant steadily decreasing with increase in Mn concentration. Martensitic transition begins to appear in Ni2Mn1.35In0.65 at about 197K and the structure seems to adopt two phases including the major cubic along with the modulated monoclinic phase. This has been explained on the basis of number of Mn-Ni-Mn hybridized pairs that are responsible for inducing martensitic transition.

  4. Microstructure of precipitates and magnetic domain structure in an annealed Co.sub.38./sub.Ni.sub.33./sub.Al.sub.29./sub. shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Bártová, Barbora; Wiese, N.; Schryvers, D.; Chapman, J. N.; Ignacová, Silvia

    2008-01-01

    Roč. 56, č. 16 (2008), 4470-4476 ISSN 1359-6454 Institutional research plan: CEZ:AV0Z10100520 Keywords : CoNiAl shape memory alloys * microstructure * precipitates * magnetic domains * Lorentz microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.729, year: 2008

  5. Mechanical and functional properties of two-phase Ni53Mn22Co6Ga19 high-temperature shape memory alloy with the addition of Dy

    International Nuclear Information System (INIS)

    Yang, S Y; Wang, C P; Liu, X J

    2013-01-01

    The effects of Dy addition on microstructure, martensitic transformation, mechanical and shape memory properties of the two-phase Ni 53 Mn 22 Co 6 Ga 19 high-temperature shape memory alloy were investigated. It is found that a small Dy addition results in the refinement of grain size, which can effectively improve the tensile ductility and strength of the two-phase Ni 53 Mn 22 Co 6 Ga 19 alloy. However, a Dy(Ni,Mn) 4 Ga precipitate forms in the alloys with the Dy addition, and its amount increases with an increase in the Dy addition. This change causes the ductility of the alloys to decrease when the Dy addition is further increased to 0.3 at.%. The results further show that the changes in the martensitic transformation temperature of the studied alloys can be attributed to the combined effects of the tetragonality (c/a) and electron concentration (e/a) of martensite. Additionally, the shape memory effects of the alloys are closely related to the refinement of grain size and the alloy strength. In this study, the (Ni 53 Mn 22 Co 6 Ga 19 ) 99.8 Dy 0.2 alloy exhibits a variety of good properties, including a high martensitic transformation starting temperature of 385.7 °C, a tensile ductility of 10.3% and a shape memory effect of 2.8%. (paper)

  6. Soldering-induced Cu diffusion and intermetallic compound formation between Ni/Cu under bump metallization and SnPb flip-chip solder bumps

    Science.gov (United States)

    Huang, Chien-Sheng; Jang, Guh-Yaw; Duh, Jenq-Gong

    2004-04-01

    Nickel-based under bump metallization (UBM) has been widely used as a diffusion barrier to prevent the rapid reaction between the Cu conductor and Sn-based solders. In this study, joints with and without solder after heat treatments were employed to evaluate the diffusion behavior of Cu in the 63Sn-37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure. The atomic flux of Cu diffused through Ni was evaluated from the concentration profiles of Cu in solder joints. During reflow, the atomic flux of Cu was on the order of 1015-1016 atoms/cm2s. However, in the assembly without solder, no Cu was detected on the surface of Ni even after ten cycles of reflow. The diffusion behavior of Cu during heat treatments was studied, and the soldering-process-induced Cu diffusion through Ni metallization was characterized. In addition, the effect of Cu content in the solder near the solder/intermetallic compound (IMC) interface on interfacial reactions between the solder and the Ni/Cu UBM was also discussed. It is evident that the (Cu,Ni)6Sn5 IMC might form as the concentration of Cu in the Sn-Cu-Ni alloy exceeds 0.6 wt.%.

  7. Quantifying the dependence of Ni(P) thickness in ultrathin-ENEPIG metallization on the growth of Cu–Sn intermetallic compounds in soldering reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Cheng-Ying; Duh, Jenq-Gong, E-mail: jgd@mx.nthu.edu.tw

    2014-11-14

    A new multilayer metallization, ENEPIG (Electroless Ni(P)/Electroless Pd/Immersion Au) with ultrathin Ni(P) deposit (ultrathin-ENEPIG), was designed to be used in high frequency electronic packaging in this study because of its ultra-low electrical impedance. Sequential interfacial microstructures of commercial Sn–3.0Ag–0.5Cu solders reflowed on ultarthin-ENEPIG with Ni(P) deposit thickness ranged from 4.79 μm to 0.05 μm were first investigated. Accelerated thermal aging test was then conducted to evaluate the long-term thermal stabilization of solder joints. The results showed that P-rich intermetallic compound (IMC) layer formed when the Ni(P) thickness was greater than a critical vale (about 0.18 μm). Besides, it is interesting to mention that the growth of (Cu,Ni){sub 6}Sn{sub 5} and (Cu,Ni){sub 3}Sn IMCs was suppressed with the formation of P-rich layer, i.e., Ni{sub 3}P and Ni{sub 2}Sn{sub 1+x}P{sub 1−x} phase, even though the electroless-plated Ni(P) layer was exhausted at initial stage of reflow process. The atomic Cu flux in solder joints without P-rich layer was calculated to be several times larger than that with P-rich layer formation after calculation, which implies that the P-rich layer and ultrathin Ni(P) deposit in ENEPIG served as diffusion barrier against rapid Cu diffusion. - Highlights: • Microstructures in ultrathin-ENEPIG with various Ni(P) thickness are investigated. • P-rich IMC layer formed when the Ni(P) thickness is greater than 0.18 μm. • Secondary (Cu,Ni){sub 6}Sn{sub 5} formed when the Ni(P) thickness is between 0.18 and 0.31 μm. • Cu diffusion flux without P-rich layer is larger than those with P-rich layer. • P-rich layer in ultrathin-ENEPIG exhibits good diffusion barrier characteristic.

  8. Comparative studies on ultrasonic, friction, laser and resistance pressure welding of NiTi shape memory alloys with high-alloy steels. Final report; Vergleichende Untersuchungen zum Ultraschall-, Reib-, Laserstrahl- und Widerstandspressschweissen von NiTi-Shape-Memory-Metall mit hochlegierten Staehlen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Zuckschwerdt, K.

    2000-04-01

    The suitability of different welding techniques for welding of NiTi shape memory alloys with high-alloy steel (C12CrNi17-7, X5CrNiNb19-9, X20Cr13) was investigated. The quality of the welds was analyzed using mechanical-technological, fractographic, metallographic and electron microscopy analysis. [German] Ziel dieses Forschungsvorhabens ist es, die Eignung der einzelnen Schweissverfahren fuer das Fuegen von NiTi-Formgedaechtnislegierungen mit hochlegiertem Stahl (X12CrNi17-7, X5CrNiNb19-9, X20Cr13) darzustellen und zu beurteilen. Die Qualitaet der Fuegeverbindungen wird mit Hilfe mechanisch-technologischer, fraktographischer, metallographischer und elektronenmikroskopischer Untersuchungen bewertet.

  9. 7-NI and ODQ Disturbs Memory in the Elevated Plus Maze, Morris Water Maze, and Radial Arm Maze Tests in Mice.

    Science.gov (United States)

    Mutlu, Oguz; Akar, Furuzan; Celikyurt, Ipek Komsuoglu; Tanyeri, Pelin; Ulak, Guner; Erden, Faruk

    2015-01-01

    Nitric oxide (NO) is an atypical neurotransmitter that causes changes in cognition. Nitric oxide synthase (NOS) and guanylate cyclase (GC) inhibitors have been shown to exert some effects on cognition in previous studies; however, the findings have been controversial. This study was aimed at understanding the effects of an NOS inhibitor, 7-nitroindazole (7-NI), and a guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), on spatial memory in modified elevated plus maze (mEPM), Morris water maze (MWM), and radial arm maze (RAM) tests. Male Balb-c mice were treated via intraperitoneal injections with 7-NI (15 mg/kg), ODQ (3, 10 mg/kg), L-arginine (100 mg/kg) + 7-NI (15 mg/kg), or physiological saline. ODQ (3 mg/kg) and 7-NI (15 mg/kg) significantly increased the second-day latency in the mEPM test. 7-NI (15 mg/kg) and ODQ (10 mg/kg) significantly increased the escape latency in second, third, and fourth sessions, decreased the time spent in the escape platform's quadrant, and increased the mean distance to the platform in the probe trial of the MWM test. ODQ (3, 10 mg/kg) and 7-NI (15 mg/kg) significantly increased the number of errors, whereas only 7-NI increased the latency in the RAM test. The administration of L-arginine (100 mg/kg) prior to 7-NI inverted the effects of 7-NI, which supports the role of NO on cognition. Our study shows that the NO/cGMP/GS pathway can regulate spatial memory in mice.

  10. 7-NI and ODQ Disturbs Memory in the Elevated plus Maze, Morris Water Maze, and Radial Arm Maze Tests in Mice

    Directory of Open Access Journals (Sweden)

    Oguz Mutlu

    2015-01-01

    Full Text Available Nitric oxide (NO is an atypical neurotransmitter that causes changes in cognition. Nitric oxide synthase (NOS and guanylate cyclase (GC inhibitors have been shown to exert some effects on cognition in previous studies; however, the findings have been controversial. This study was aimed at understanding the effects of an NOS inhibitor, 7-nitroindazole (7-NI, and a guanylate cyclase inhibitor, 1 H -[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, on spatial memory in modified elevated plus maze (mEPM, Morris water maze (MWM, and radial arm maze (RAM tests. Male Balb-c mice were treated via intraperitoneal injections with 7-NI (15 mg/kg, ODQ (3, 10 mg/kg, L-arginine (100 mg/kg + 7-NI (15 mg/kg, or physiological saline. ODQ (3 mg/kg and 7-NI (15 mg/kg significantly increased the second-day latency in the mEPM test. 7-NI (15 mg/kg and ODQ (10 mg/kg significantly increased the escape latency in second, third, and fourth sessions, decreased the time spent in the escape platform's quadrant, and increased the mean distance to the platform in the probe trial of the MWM test. ODQ (3, 10 mg/kg and 7-NI (15 mg/kg significantly increased the number of errors, whereas only 7-NI increased the latency in the RAM test. The administration of L-arginine (100 mg/kg prior to 7-NI inverted the effects of 7-NI, which supports the role of NO on cognition. Our study shows that the NO/cGMP/GS pathway can regulate spatial memory in mice.

  11. Molecular Bases of PDE4D Inhibition by Memory-Enhancing GEBR Library Compounds.

    Science.gov (United States)

    Prosdocimi, Tommaso; Mollica, Luca; Donini, Stefano; Semrau, Marta S; Lucarelli, Anna Paola; Aiolfi, Egidio; Cavalli, Andrea; Storici, Paola; Alfei, Silvana; Brullo, Chiara; Bruno, Olga; Parisini, Emilio

    2018-05-01

    Selected members of the large rolipram-related GEBR family of type 4 phosphodiesterase (PDE4) inhibitors have been shown to facilitate long-term potentiation and to improve memory functions without causing emetic-like behavior in rodents. Despite their micromolar-range binding affinities and their promising pharmacological and toxicological profiles, few if any structure-activity relationship studies have been performed to elucidate the molecular bases of their action. Here, we report the crystal structure of a number of GEBR library compounds in complex with the catalytic domain of PDE4D as well as their inhibitory profiles for both the long PDE4D3 isoform and the catalytic domain alone. Furthermore, we assessed the stability of the observed ligand conformations in the context of the intact enzyme using molecular dynamics simulations. The longer and more flexible ligands appear to be capable of forming contacts with the regulatory portion of the enzyme, thus possibly allowing some degree of selectivity between the different PDE4 isoforms.

  12. Atomic mobility in the overheated amorphous GeTe compound for phase change memories

    International Nuclear Information System (INIS)

    Sosso, G.C.; Behler, J.; Bernasconi, M.

    2016-01-01

    Abstractauthoren Phase change memories rest on the ability of some chalcogenide alloys to undergo a fast and reversible transition between the crystalline and amorphous phases upon Joule heating. The fast crystallization is due to a high nucleation rate and a large crystal growth velocity which are actually possible thanks to the fragility of the supercooled liquid that allows for the persistence of a high atomic mobility at high supercooling where the thermodynamical driving force for crystallization is also high. Since crystallization in the devices occurs by rapidly heating the amorphous phase, hysteretic effects might arise with a different diffusion coefficient and viscosity on heating than on cooling. In this work, we have quantified these hysteretic effects in the phase change compound GeTe by means of molecular dynamics simulations. The atomic mobility in the overheated amorphous phase is lower than in supercooled liquid at the same temperature and the viscosity is consequently higher. Still, the simulations of the overheated amorphous phase reveal a breakdown of the Stokes-Einstein relation between the diffusion coefficient and the viscosity, similarly to what we found previously in the supercooled liquid. Evidences are provided that the breakdown is due to the emergence of dynamical heterogeneities at high supercooling. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Energy landscape for martensitic phase transformation in shape memory NiTi

    International Nuclear Information System (INIS)

    Kibey, S.; Sehitoglu, H.; Johnson, D.D.

    2009-01-01

    First-principles calculations are presented for parent B2 phase and martensitic B19 and B19' phases in NiTi. The results indicate that both B19 and B19' are energetically more stable than the parent B2 phase. By means of ab initio density functional theory, the complete distortion-shuffle energy landscape associated with B2 → B19 transformation in NiTi is then determined. In addition to accounting for the Bain-type deformation through the Cauchy-Born rule, the study explicitly accounts for the shuffle displacements experienced by the internal ions in NiTi. The energy landscape allows the energy barrier associated with the B2 → B19 transformation pathway to be identified. The results indicate that a barrier of 0.48 mRyd atom -1 (relative to the B2 phase) must be overcome to transform the parent B2 NiTi to orthorhombic B19 martensite

  14. On the multiplication of dislocations during martensitic transformations in NiTi shape memory alloys

    Czech Academy of Sciences Publication Activity Database

    Simon, T.; Kröger, A.; Somsen, Ch.; Dlouhý, Antonín; Eggeler, G.

    2010-01-01

    Roč. 58, č. 5 (2010), s. 1850-1860 ISSN 1359-6454 R&D Projects: GA ČR GA106/09/1913 Institutional research plan: CEZ:AV0Z20410507 Keywords : NiTi * Martensitic transformations * Dislocation multiplication mechanism * Martensite variants * Dislocations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.781, year: 2010

  15. Structure changes of Co-Ni-Al ferromagnetic shape memory alloys after vacuum annealing and hot rolling

    International Nuclear Information System (INIS)

    Maziarz, Wojciech

    2008-01-01

    The structure changes of vacuum annealed and hot rolled Co 35+x -Ni 40-x -Al 25 (x = 0, 2.5, 5.0) ferromagnetic shape memory alloys were examined by optical microscopy and X-ray diffraction measurements. Almost the same content of γ phase was observed in alloys after vacuum annealing. The change of grains morphology from dendrite in to equiaxed ones appeared after vacuum annealing. The hot rolling process was applied after annealing at 900 deg. C with thickness reduction up to about 90%. The structure of hot rolled samples revealed elongated grains of different phases. The hardness changes after heat treatment and plastic deformation processes have reflected the solution hardening and work hardening, respectively

  16. Phonon dispersion in the ferromagnetic shape memory alloy Ni2MnGa studied by neutron spectroscopy

    International Nuclear Information System (INIS)

    Vorderwisch, P.; Shapiro, S.M.

    2006-01-01

    Neutron spectroscopy is an ideal technique to study the structure and dynamics of crystals. For the ferromagnetic shape memory alloy Ni 2 MnGa, all previously obtained information from inelastic neutron scattering experiments is restricted to the phonon dispersion in the austenitic (fcc) phase of alloys with different compositions. For the (tetragonally distorted) martensitic phase recent inelastic neutron scattering data are presented. These new data were taken on a single crystal with stoichiometric composition. A single-variant martensitic phase of the sample has been obtained by the application of magnetic fields in horizontal or vertical direction with respect to the scattering plane used in the experiments. The measured phonon-dispersion curves are compared with recently published ab initio (zero-temperature) phonon-dispersion calculations. The anomalous phonon behavior observed in both, the austenitic and martensitic phase is discussed

  17. Macroscopic and Microstructural Aspects of the Transformation Behavior in a Polycrystalline NiTi Shape Memory Alloy

    Science.gov (United States)

    Benafan, Othmane; Noebe, Ronald D.; Padula, Santo A., II; Lerch, Bradley A.; Bigelow, Glen S.; Gaydosh, Darrell J.; Garg, Anita; An, Ke; Vaidyanathan, Raj

    2013-01-01

    The mechanical and microstructural behavior of a polycrystalline Ni(49.9)Ti(50.1) (at.%) shape memory alloy was investigated as a function of temperature around the transformation regime. The bulk macroscopic responses, measured using ex situ tensile deformation and impulse excitation tests, were compared to the microstructural evolution captured using in situ neutron diffraction. The onset stress for inelastic deformation and dynamic Young's modulus were found to decrease with temperature, in the martensite regime, reaching a significant minimum at approximately 80 C followed by an increase in both properties, attributed to the martensite to austenite transformation. The initial decrease in material compliance during heating affected the ease with which martensite reorientation and detwinning could occur, ultimately impacting the stress for inelastic deformation prior to the start of the reverse transformation.

  18. Effect of Magnetostatic Interactions on Twin Boundary Motion in NiMnGa Magnetic Shape Memory Alloy

    DEFF Research Database (Denmark)

    Heczko, Oleg; Vokoun, David; Kopecky, Vit

    2015-01-01

    on the initial position of the twin boundary, the magnetic field providing the critical stress varied in the range 832 kA/m. By taking into account the variants sizes and their mutual interactions, we explained the observed dependence of the switching field on the location of the boundary. The resulting match......We investigated the effect of magnetostatic interactions on the field-induced reorientation of martensite variants in Ni50.0Mn27.5Ga22.5. The reorientation, achieved by sweeping a single Type-II twin boundary along the sample, was triggered by a twinning stress of about 0.1 MPa. However, depending...... between model predictions and measurements illustrates the fundamental role played by demagnetization effects and magnetostatic interactions in magnetic shape memory effect....

  19. Three-dimensional modeling for deformation of austenitic NiTi shape memory alloys under high strain rate

    Science.gov (United States)

    Yu, Hao; Young, Marcus L.

    2018-01-01

    A three-dimensional model for phase transformation of shape memory alloys (SMAs) during high strain rate deformation is developed and is then calibrated based on experimental results from an austenitic NiTi SMA. Stress, strain, and martensitic volume fraction distribution during high strain rate deformation are simulated using finite element analysis software ABAQUS/standard. For the first time, this paper presents a theoretical study of the microscopic band structure during high strain rate compressive deformation. The microscopic transformation band is generated by the phase front and leads to minor fluctuations in sample deformation. The strain rate effect on phase transformation is studied using the model. Both the starting stress for transformation and the slope of the stress-strain curve during phase transformation increase with increasing strain rate.

  20. Superelastic NiTi memory alloy micro-tube under tension - nucleation and propagation of martensite band

    International Nuclear Information System (INIS)

    Li, Z.Q.; Sun, Q.P.

    2000-01-01

    The superelastic behavior of polycrystalline NiTi shape memory alloy micro-tube under tension is studied experimentally. The nominal stress-strain curve of the micro-tube is recorded. By using a special surface coating it is found that the deformation of the tube is via the nucleation and propagation of stress-induced martensite band. The experiments show that the martensite nucleates in the form of a spiral lens-shaped narrow band that is inclined at 61 to the axis of loading when the stress reaches the peak of stress-strain curve. The width and the length of the band grew gradually with increase of loading and finally joined and merged into a single band. The subsequent deformation of the tube is realized by the propagation of this cylindrical martensite band. (orig.)

  1. Experimental evidence of stress-field-induced selection of variants in Ni-Mn-Ga ferromagnetic shape-memory alloys

    International Nuclear Information System (INIS)

    Wang, Y. D.; Brown, D. W.; Choo, H.; Liaw, P. K.; Benson, M. L.; Cong, D. Y.; Zuo, L.

    2007-01-01

    The in situ time-of-flight neutron-diffraction measurements captured well the martensitic transformation behavior of the Ni-Mn-Ga ferromagnetic shape-memory alloys under uniaxial stress fields. We found that a small uniaxial stress applied during phase transformation dramatically disturbed the distribution of variants in the product phase. The observed changes in the distributions of variants may be explained by considering the role of the minimum distortion energy of the Bain transformation in the effective partition among the variants belonging to the same orientation of parent phase. It was also found that transformation kinetics under various stress fields follows the scale law. The present investigations provide the fundamental approach for scaling the evolution of microstructures in martensitic transitions, which is of general interest to the condensed matter community

  2. Orientation dependence of stress-induced martensite formation during nanoindentation in NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Laplanche, G.; Pfetzing-Micklich, J.; Eggeler, G.

    2014-01-01

    In the present work we used nanoindentation with a spherical indenter tip to study the formation of stress-induced martensite in NiTi shape memory alloys. Prior to nanoindentation, orientation imaging was performed to select austenite grains with specific crystallographic orientations, including the principal crystallographic directions [0 0 1], [1 0 1] and [1 1 1]. We studied a material where stress-induced martensite is stable at room temperature and found surface patterns with four-, two- and threefold symmetries for the [0 0 1], [1 0 1] and [1 1 1] crystallographic indentation directions, respectively. Atomic force microscopy investigations of the topography showed that the surface patterns were associated with sink-ins. The crystallographic sink-in patterns disappeared during heating, which proved their martensitic origin. Our results provide clear experimental evidence which shows that the crystallographic anisotropy of nanoindentation is governed by the crystallographic anisotropy of the stress-induced formation of martensite

  3. Texture development and strain hysteresis in a NiTi shape-memory alloy during thermal cycling under load

    International Nuclear Information System (INIS)

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

    2009-01-01

    Thermal cycling experiments were conducted on a NiTi shape-memory alloy at different constant applied stresses below the yield strength of the martensite. The mechanical strain response manifested as strain hysteresis loops, whose range was proportional to the applied stress. In situ neutron diffraction experiments show that the strain hysteresis occurs as a result of the establishment of a stress-dependent crystallographic texture of the martensite during the first cool-down from austenite, and thereafter repeated during thermal cycling under the same load. This texture is found to depend on the stress during the thermal cycling experiments. A strain-pole map is derived and shown to explain the observed texture during thermal cycling. The strain-pole methodology is shown to work with similar martensitic transformations in other material systems.

  4. Internal friction behaviors of Ni-Mn-In magnetic shape memory alloy with two-step structural transformation

    Directory of Open Access Journals (Sweden)

    Zhen-ni Zhou

    2017-06-01

    Full Text Available The internal friction (IF behaviors of dual-phase Ni52Mn32In16 alloy with two-step structural transformation were investigated by dynamic mechanical analyzer. The IF peak for the martensite transformation (MT is an asymmetric shoulder rather than those sharp peaks for other shape memory alloys. The intermartensitic transformation (IMT peak has the maximum IF value. As the heating rate increases, the height of the IMT peak increases and its position is shifted to higher temperatures. In comparison with the IMT peak, the MT peak is independent on the heating rate. The starting temperatures of the IMT peak are strongly dependent on frequency, while the MT peak is weakly dependent. Meanwhile, the heights of both the MT and IMT peak rapidly decrease with increasing the frequency. This work also throws new light on their structural transformation mechanisms.

  5. Characterization and study of the behavior of wire Ti-Ni with shape memory effect enables manufacture of actuators

    International Nuclear Information System (INIS)

    Pina, E.A.C.; Araujo Filho, O.O. de; Urtiga Filho, S.L.; Gonzalez, C.H.

    2010-01-01

    This work aims to characterize the wire commercial Ti-Ni of 1.27 mm in diameter with shape memory effect for the development of helical springs with the function of sensor / actuator. After heat treatment, the transformation temperatures, the presence of precipitates, the degree of damping, maximum stress of rupture, modulus of elasticity, the presence of phase R, the behavior of the alloy under tension, will be analyzed and compared in each situation. For characterization we used several methods including: heat treatment, Differential Scanning Calorimetry (DSC), tensile, dynamic mechanical analysis (DMA), X-ray diffraction, thermomechanical cycling. The wires were cut into pieces and heat-treated at 400 deg C with variation of time in muffle furnaces and quenching in water at 25 deg C. (author)

  6. Transformation Paths from Cubic to Low-Symmetry Structures in Heusler Ni2MnGa Compound.

    Science.gov (United States)

    Zelený, Martin; Straka, Ladislav; Sozinov, Alexei; Heczko, Oleg

    2018-05-08

    In order to explain the formation of low-temperature phases in stoichiometric Ni 2 MnGa magnetic shape memory alloy, we investigate the phase transformation paths from cubic austenite with Heusler structure to low-symmetry martensitic structures. We used ab initio calculations combined with the generalized solid state nudged elastic band method to determine the minimum energy path and corresponding changes in crystal lattice. The four-, five-, and seven-layered modulated phases of martensite (4O, 10M, and 14M) are built as the relaxed nanotwinned non-modulated (NM) phase. Despite having a total energy larger than the other martensitic phases, the 10M phase will spontaneously form at 0 K, because there is no energy barrier on the path and the energy decreases with a large negative slope. Moreover, a similar negative slope in the beginning of path is found also for the transformation to the 6M premartensite, which appears as a local minimum on the path leading further to 10M martensite. Transformation paths to other structures exhibit more or less significant barriers in the beginning hindering such a transformation from austenite. These findings correspond to experiment and demonstrates that the kinetics of the transformation is decisive for the selection of the particular low-symmetry structure.

  7. Wafer-level integration of NiTi shape memory alloy on silicon using Au–Si eutectic bonding

    International Nuclear Information System (INIS)

    Gradin, Henrik; Bushra, Sobia; Braun, Stefan; Stemme, Göran; Van der Wijngaart, Wouter

    2013-01-01

    This paper reports on the wafer level integration of NiTi shape memory alloy (SMA) sheets with silicon substrates through Au–Si eutectic bonding. Different bond parameters, such as Au layer thicknesses and substrate surface treatments were evaluated. The amount of gold in the bond interface is the most important parameter to achieve a high bond yield; the amount can be determined by the barrier layers between the Au and Si or by the amount of Au deposition. Deposition of a gold layer of more than 1 μm thickness before bonding gives the most promising results. Through patterning of the SMA sheet and by limiting bonding to small areas, stresses created by the thermal mismatch between Si and NiTi are reduced. With a gold layer of 1 μm thickness and bond areas between 200 × 200 and 800 × 800 μm 2 a high bond strength and a yield above 90% is demonstrated. (paper)

  8. Effect of Chemical Composition on The Microstructure and High-Temperature Properties of Ti-Ni-Hf High-Temperature Shape Memory Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Seong-Woo; Lee, Hak-Sung; Jeon, Yeong-Min; Yeom, Jong-Taek; Kim, Seong-Woong; Park, Chan-Hee; Hong, Jae-Keun; Oh, Chang-Seok [Korea Institute of Materials Science, Changwon (Korea, Republic of); Nam, Tae-Hyun [Gyeongsang National University, Jinju (Korea, Republic of); Kim, Jeoung Han [Hanbat National University, Daejeon (Korea, Republic of)

    2015-03-15

    The effect of Ni and Hf content on the microstructure, phase transformation, and hot workability of Ti-Ni-Hf high-temperature shape memory alloys (SMAs) were investigated. Twelve different Ti-xNi (x=49, 50.2, 50.5, 50.8 at%)-yHf (y=10, 12, 14 at%) SMA ingots were prepared by vacuum arc re-melting, and then analyzed by SEM, DSC, TEM, and XRD after heat treatment. Precipitation behavior was mostly dependent on Ni content rather than Hf content. The effect of homogenization treatment on the particle precipitation and phase transformation behavior was studied. We also found that hot workability was greatly dependent on the solidification structure of the austenite phase.

  9. Evaluation of the interfacial shear strength between pseudoplastic NiTi shape memory alloy wires and epoxy by the pull-out method

    International Nuclear Information System (INIS)

    Spārniņš, E; Michaud, V; Leterrier, Y; Andersons, J

    2015-01-01

    The interfacial shear strength (IFSS) between nickel–titanium (NiTi) shape memory alloy wires, characterized by a nonlinear stress–strain behavior, and epoxy matrix was determined by pull-out tests. Tests were carried out at several temperatures and levels of pre-strain in the wires, to evaluate the effects of embedded wire length and of crystalline state of the alloy. The IFSS between the twinned NiTi and epoxy was estimated at 24 MPa, and found to increase to 47 MPa for completely detwinned and preloaded martensitic NiTi. This increase in IFSS values was attributed to microcracking of the superficial TiO 2 layer and the resulting roughening of the NiTi wire surface. (paper)

  10. Creation of submicrocrystalline structure and enhancing of functional properties of Ti-Ni-Fe alloys with the shape-memory effect using equichannel-angular pressing (ECAP)

    International Nuclear Information System (INIS)

    Prokoshkin, S.D.; Belousov, M.N.; Abramov, V.Ya.

    2007-01-01

    Methods of X-ray diffraction analysis, transmission electron microscopy, mechanical and thermomechanical tests are used to study structure, mechanical and service properties of Ti-Ni-Fe system shape memory alloys (Ti-47.6 % Ni-2.4 % Fe; Ti-47 % Ni-3 % Fe; Ti-46.6 % Ni-3.4 % Fe). The alloys are subjected to hardening, high temperature thermomechanical treatment (HTMT) and equal-channel angular pressing (EChAP). Thermomechanical connecting pieces of given alloys are tested for carrying capacity and low temperature stability. It is established that the use of EChAP and post-deformation annealing at pressing temperature provides more high properties of the alloys in comparison with hardening and HTMT [ru

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

    International Nuclear Information System (INIS)

    Trochu, F.; Sacepe, N.; Volkov, O.; Turenne, S.

    1999-01-01

    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.)

  12. Effect of heat treatment on the crystal structure, martensitic transformation and magnetic properties of Mn{sub 53}Ni{sub 25}Ga{sub 22} ferromagnetic shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dong, G.F., E-mail: dgfu0451@sina.com [Department of mechanics Dalian University, Dalian 116622 (China); Gao, Z.Y. [National Key Laboratory Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, P.O. Box 405, Harbin 150001 (China)

    2016-02-01

    In this study, the effect of heat treatment on crystal structure, martensitic transformation, thermodynamic behavior and magnetic properties of polycrystalline Mn{sub 53}Ni{sub 25}Ga{sub 22} ferromagnetic shape memory alloy was systematically investigated. The results show that the heat treatment has obvious effect on martensitic transformation temperatures, crystal structure and hysteresis loops. Heat treatment greatly effects on transformation temperatures due to modified composition of the matrix. Martensitic transformation temperature, saturation magnetization decreased with the increase heat treatment temperature, reaching their minimum values at the heat treatment temperature of 1173 K for 12 h. Curie temperature of maximum values obtained at solution-treated of 1173 K for 12 h. In other word, increasing heat treatment temperature and time has an effect on Curie temperature. In addition, the annealed alloy Mn{sub 53}Ni{sub 25}Ga{sub 22} may completely dissolve in vacuum tubes at 1173 K for 12 h. It is found that the studied alloys have some (Mn,Ni){sub 4} Ga-type compound precipitates, which can be seen dispersing both in grain interiors and on grain boundaries at other heat treatment process. Lastly, Rietveld analysis shows the good agreement between experiment and calculated data of XRD patterns. - Highlights: • Heat treatment has obvious effect on transformation, structure and hysteresis. • Transformation temperature decreased with increase heat treatment temperature. • Magnetization decreased with increase heat treatment temperature. • Annealed alloy completely dissolve in vacuum tubes at 1123 K for 24 h.

  13. Realization of transient memory-loss with NiO-based resistive switching device

    Science.gov (United States)

    Hu, S. G.; Liu, Y.; Chen, T. P.; Liu, Z.; Yu, Q.; Deng, L. J.; Yin, Y.; Hosaka, Sumio

    2012-11-01

    A resistive switching device based on a nickel-rich nickel oxide thin film, which exhibits inherent learning and memory-loss abilities, is reported in this work. The conductance of the device gradually increases and finally saturates with the number of voltage pulses (or voltage sweepings), which is analogous to the behavior of the short-term and long-term memory in the human brain. Furthermore, the number of the voltage pulses (or sweeping cycles) required to achieve a given conductance state increases with the interval between two consecutive voltage pulses (or sweeping cycles), which is attributed to the heat diffusion in the material of the conductive filaments formed in the nickel oxide thin film. The phenomenon resembles the behavior of the human brain, i.e., forgetting starts immediately after an impression, a larger interval of the impressions leads to more memory loss, thus the memorization needs more impressions to enhance.

  14. Improving the Performance of Electrically Activated NiTi Shape Memory Actuators by Pre-Aging

    Science.gov (United States)

    Rathmann1, Christian; Fleczok1, Benjamin; Otibar1, Dennis; Kuhlenkötter, Bernd

    2017-06-01

    Shape memory alloys possess an array of unique functional properties which are influenced by a complex interaction of different factors. Due to thermal sensitivity, slight changes in temperature may cause the properties to change significantly. This poses a huge challenge especially for the use of shape memory alloys as actuators. The displacement is the key performance indicator, which has to be of equal or better quality compared to conventional actuators. One problem of shape memory alloys is the change in functional fatigue in the first cycles, which makes it rather difficult to design the actuator. Therefore, the reduction of this shakedown effect is crucial. For this reason, this paper investigates the effect of electrical heat treatment as a method for pre-aging. This topic has so far been little investigated so that the investigations focus on identifying important factors and effects by using the design of experiments.

  15. Effects of Compound Yi-Zhi on D-galactose-induced learning and memory deficits in mice

    Institute of Scientific and Technical Information of China (English)

    XUJiang-Ping; WUHang-Yu; LILin

    2004-01-01

    AIM: To explore the effects of Compound Yi-Zhi (YZC) on learning and memory capacity and free radical metabolism in D-galactose induced mice dementia model. METHODS: The mice dementia model was induced by a daily D-galactose 0.15g/kg sc for 45 days and after 5 days'D-galactose injection, the mice were treated with three doses of YZC

  16. One step hydrogenation–esterification of model compounds and bio-oil to alcohols and esters over Raney Ni catalysts

    International Nuclear Information System (INIS)

    Xu, Ying; Zhang, Limin; Chang, Jiamin; Zhang, Xinghua; Ma, Longlong; Wang, Tiejun; Zhang, Qi

    2016-01-01

    Highlights: • Fe–RN and Mo–RN showed excellent inhibition of alkylation and hydrogenation activity of phenol respectively. • The esterification activity of alcohols with acetic acid was followed as methanol > THFA > ethanediol. • After OHE of bio-oil, the total content of alcohols and esters reached to 87.27% in the product. - Abstract: Acids, aldehydes, ketones and phenols, which are the main components of bio-oil, have negative effects on the properties. In this paper, the mixture of acetic acid, furfural, hydroxyacetone, ethanediol, phenol and water were chosen as hybrid model compounds of bio-oil (MCB). To convert these compounds into stable and combustible oxygenated organics (alcohols and esters), one step hydrogenation–esterification (OHE) was carried out over Raney Ni catalyst (RN) and Mo, Sn, Fe, Cu modified Raney Ni catalysts (RNs) in the presence of methanol. 100% conversions of furfural and hydroxyacetone were achieved over RNs with high selectivity to desired products. The acetic acid conversion was only 35.1% with no methanol addition, while within 6 g/8 g methanol/MCB addition, the conversion of acetic acid increased to 81.1%. The esterification activity of alcohols was followed by methanol > tetrahydrofurfuryl alcohol (THFA), the hydrogenation product of furfural > ethanediol. Among the RNs, the addition of Fe catalyst restrained the aqueous-phase reforming of methanol and promoted the esterification of methanol and acetic acid. The Mo–RN showed the most favorable performance in the hydrogenation of phenol among the RNs. But the RN modified by both Fe and Mo did not give a good performance. After the OHE of light fraction of raw bio-oil over Mo–RN, there was no ketone & aldehyde detected and the contents of acids and phenols decreased from 49.04% and 7.35% to 8.21% and 3.84%. The conversion of acids could reach to 85.01% which was nearly to the conversion of acetic acid in MCB. The contents of alcohols and esters increased from 5

  17. Negative and Zero Thermal Expansion NiTi Superelastic Shape Memory Alloy by Microstructure Engineering

    Science.gov (United States)

    Sun, Qingping; Yu, Chao; Kang, Guozheng

    2018-03-01

    We report recent progress in tailoring the thermal expansion (TE) of nanocrystalline (NC) NiTi by microstructure hierarchical design and control without composition change. Fabrication and characterization methods are outlined and preliminary results of both experiment and mechanism-based modeling are presented to understand and get insight into the unusual TE phenomena. The important roles of the intrinsic thermal expansion anisotropy of B19' lattice and the suppression of phase transition by the extrinsic fabricated microstructure (cold rolling and annealing, grain size, defects, textures and volume fractions of nanoscaled B2 and B19' lattices) in the overall macroscopic TE behaviors of the superelastic NC NiTi polycrystal SMAs are emphasized.

  18. Limitations of constitutive relations for TiNi shape memory alloys

    International Nuclear Information System (INIS)

    Tang, W.; Sandstroem, R.

    1995-01-01

    Phase transformation tensor Ω in the constitutive equation proposed by Tanaka has been evaluated by employing experimental data of TiNi alloys in a constrained recovery process. It demonstrates that the absolute value of Ω for the constrained recovery process is typically about 0.6 ∼ 0.7 x 10 3 MPa, which is much smaller than that for the stress - induced martensitic transformation (typically 2.5 ∼ 3.5 x 10 3 ). Based on the evaluated results for Ω, predicted recovery stress - temperature relations by the constitutive equation are compared with the experimental data for TiNi rods under different strains. Big discrepancy exists for large strain conditions. Several transformation kinetic expressions are examined for the constitutive relation of the constrained recovery process. (orig.)

  19. The martensitic transformation of Ti–Ni shape memory thin films under proton irradiation

    International Nuclear Information System (INIS)

    Gao, Z.Y.; Wang, H.Z.; Zhu, Y.Y.; Meng, X.L.; Cai, W.

    2015-01-01

    The martensitic transformation behavior of a Ti–Ni alloy irradiated by proton with different doses has been investigated. It is found that the samples irradiated by 150 keV protons have a two-step phase transformation during heating and only one-step transformation during cooling. The exothermic peak at higher temperature disappears during the following thermal cycling. A model based on the stress-assisted martensitic transformation was established by the Transport of Ions in Matter (TRIM) calculations in order to explain the transformation behavior. - Highlights: • Martensitic transformation behavior of TiNi alloy under proton irradiation • Two-step transformation appears upon heating for a sample irradiated at 150 keV. • One-step transformation appears upon cooling for a sample irradiated at 150 keV. • In the following thermal cycling, the higher temperature exothermic peak vanishes

  20. Negative and Zero Thermal Expansion NiTi Superelastic Shape Memory Alloy by Microstructure Engineering

    Science.gov (United States)

    Sun, Qingping; Yu, Chao; Kang, Guozheng

    2018-02-01

    We report recent progress in tailoring the thermal expansion (TE) of nanocrystalline (NC) NiTi by microstructure hierarchical design and control without composition change. Fabrication and characterization methods are outlined and preliminary results of both experiment and mechanism-based modeling are presented to understand and get insight into the unusual TE phenomena. The important roles of the intrinsic thermal expansion anisotropy of B19' lattice and the suppression of phase transition by the extrinsic fabricated microstructure (cold rolling and annealing, grain size, defects, textures and volume fractions of nanoscaled B2 and B19' lattices) in the overall macroscopic TE behaviors of the superelastic NC NiTi polycrystal SMAs are emphasized.

  1. Effect of thermal cycling on the transformation temperature ranges of a Ni-Ti shape memory alloy

    International Nuclear Information System (INIS)

    Paula, A.S.; Canejo, J.P.H.G.; Martins, R.M.S.; Braz Fernandes, F.M.

    2003-01-01

    Shape memory alloys (SMA) represents a class of metallic materials that has the capability of recovering a previously defined initial shape when subject to an adequate thermomechanical treatment. The present work aims to study the influence of thermal cycles on the transition temperatures of a Ni-Ti alloy. In this system, small variations around the equiatomic composition give rise to significant transformation temperature variations ranging from 173 to 373 K. SMA usually presents the shape memory effect after an annealing treatment at ca. 973 K. The optimisation of the thermomechanical treatment will allow to 'tune' the material to different transformation temperature ranges from the same starting material, just by changing the processing conditions. Differential scanning calorimeter (DSC) and in situ high-temperature X-ray diffraction (XRD) have been used to identify the transformation temperatures and the phases that are present after different thermal cycles. The results concerning a series of thermal cycles with different heating and cooling rates (from 1.67x10 -2 to 1.25x10 -1 K/s) and different holding temperatures (from 473 to 1033 K) are presented

  2. P-phase precipitation and its effect on martensitic transformation in (Ni,Pt)Ti shape memory alloys

    International Nuclear Information System (INIS)

    Gao, Y.; Zhou, N.; Yang, F.; Cui, Y.; Kovarik, L.; Hatcher, N.; Noebe, R.; Mills, M.J.; Wang, Y.

    2012-01-01

    A new precipitate phase named P-phase has recently been identified in (Ni,Pt)Ti high temperature shape memory alloys. In order to understand the roles played by the fine coherent P-phase precipitates in determining the martensitic transformation temperature (M s ), strength of the B2 matrix phase, dimensional stability and shape memory effect of the alloys, a phase field model of P-phase precipitation is developed. Model inputs, including lattice parameters, precipitate–matrix orientation relationship, elastic constants and free energy data, are obtained from experimental characterization, ab initio calculations and thermodynamic databases. Through computer simulations, the shape and spatial distribution of the P-phase precipitates, as well as the compositional and stress fields around them, are quantitatively determined. On this basis, the elastic interaction energy between the P-phase precipitates and a martenstic nucleus is calculated. It is found that both the chemical non-uniformity and stress field associated with the P-phase precipitates are in favor of the martensitic transformation. Their relative contributions to the increase in M s temperature are quantified as a function of aging time and the result seems to agree with the experimental measurements. The shape and spatial distribution of the P-phase precipitates predicted by the simulations also agree well with experimental observations.

  3. Formation process of lamella structures by deformation in an Fe-Mn-Si-Cr-Ni shape memory alloy

    International Nuclear Information System (INIS)

    Kikuchi, T.; Kajiwara, S.; Tomota, Y.

    1995-01-01

    For Fe-Mn-Si-Cr-Ni shape memory alloys, it was previously found by HREM study that the formation of the nanometric lamella structures consisting of f.c.c. and h.c.p. phase is very important to exhibit good shape memory effect. In the present work, the formation process of such lamella structures has been studied in detail. The results are as follows. The transformation is initiated by random formation of extremely thin martensite plates with 1-2 nm width and then these plates are clustered and some of them coalesce to form thicker martensite plates with increasing deformation. The clustered regions are 400-600 nm wide and will correspond to the above mentioned lamella structures. These clustered regions are considered also to correspond to the thinnest martensite plate observable with optical microscope. In the optical microscopic scale, the thin martenite plates with the smallest width are formed rather uniformly in an austenite grain, and with further increasing deformation, they are clustered and coalesce into thicker plates with 3-8 μm width. (orig.)

  4. PIIID-formed (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti coatings on NiTi shape memory alloy for medical applications

    Energy Technology Data Exchange (ETDEWEB)

    Sun Tao, E-mail: taosun@hotmail.com.hk [Department of Mechanical Engineering, University of Hong Kong, Pokfulam Road (Hong Kong); Institute of Microelectronics, Agency for Science, Technology and Research (A-STAR) (Singapore); Wang Langping, E-mail: aplpwang@hit.edu.cn [State Key Lab of Advanced Welding and Joining, Harbin Institute of Technology (China); Wang Min; Tong Howang [Department of Mechanical Engineering, University of Hong Kong, Pokfulam Road (Hong Kong); Lu, William W. [Department of Orthopedics and Traumatology, University of Hong Kong, Sassoon Road (Hong Kong)

    2012-08-01

    (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti composite coatings were fabricated on NiTi shape memory alloy via plasma immersion ion implantation and deposition (PIIID). Surface morphology of samples was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross-sectional morphology indicated that the PIIID-formed coatings were dense and uniform. X-ray diffraction (XRD) was used to characterize the phase composition of samples. X-ray photoelectron spectroscopy (XPS) results showed that the surface of coated NiTi SMA samples was Ni-free. Nanoindentation measurements and pin-on-disc tests were carried out to evaluate mechanical properties and wear resistance of coated NiTi SMA, respectively. For the in vitro biological assessment of the composite coatings in terms of cell morphology and cell viability, osteoblast-like SaOS-2 cells and breast cancer MCF-7 cells were cultured on NiTi SMA samples, respectively. SaOS-2 cells attached and spread better on coated NiTi SMA. Viability of MCF-7 cells showed that the PIIID-formed composite coatings were noncytotoxic and coated samples were more biocompatible than uncoated samples. - Highlights: Black-Right-Pointing-Pointer PIIID-formed coatings were fabricated on NiTi SMA to improve its biocompatibility. Black-Right-Pointing-Pointer Microstructure, mechanical properties and biocompatibility of coatings were investigated. Black-Right-Pointing-Pointer All PIIID-formed composite coatings were noncytotoxic and cytocompatible.

  5. Memory

    Science.gov (United States)

    ... it has to decide what is worth remembering. Memory is the process of storing and then remembering this information. There are different types of memory. Short-term memory stores information for a few ...

  6. Mechanical and microstructural properties of Cu-Al-Ni-Mn-Zr shape memory alloy processed by spray forming

    Energy Technology Data Exchange (ETDEWEB)

    Cava, R.D.; Bolfarini, C.; Kiminami, C.S.; Mazzer, E.M.; Pedrosa, V.M.; Botta, W.J.; Gargarella, P. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil)

    2016-07-01

    Full text: Cu-based shape memory alloys (SMA) presents higher thermal and electrical conductivities, low material cost and combine good mechanical properties with a pronounced shape memory effect [1]. By using rapid solidification methods, their microstructure is refined and detrimental segregations can be avoided, which results in better mechanical properties. Additionally, the microalloying additions as Ti, B, Si and Zr can refine the grains and improve of mechanical and thermal properties of Cu-based SMA alloys [2-4]. In this investigation the Cu81.95Al11.35Ni3.2Mn3Zr0.5 (wt%) SMA alloy has been processed by spray forming in order to investigate the potential of achieving a deposit with adequate microstructure with goal to a SMA part production. The alloy was atomized with nitrogen gas at pressure of 0.5MPa. The microstructure of the deposit was characterized by optical and scanning electron microscopy and X-ray diffraction. The deposit presented homogeneous microstructure consisting of equiaxial grains with martensite microstructure and mean grain size of 30 ?m. The shape memory effect and the temperatures transformation have been evaluated by differential scanning calorimetric. The mechanical properties were evaluated by tensile and compression tests at room and at 220 deg C(T>Af) temperatures. [1] T. Waitz, et al., T, J. of the Mechanics and Physics of Solids, 55, 2007. [2] D. W. Roh, et al., Metall Trans. A, 21, 1990. [3] D. W. Roh, et al., Mat. Sci. and Eng. A136, 1991. (author)

  7. The effect of intermetallic compound morphology on Cu diffusion in Sn-Ag and Sn-Pb solder bump on the Ni/Cu Under-bump metallization

    Science.gov (United States)

    Jang, Guh-Yaw; Duh, Jenq-Gong

    2005-01-01

    The eutectic Sn-Ag solder alloy is one of the candidates for the Pb-free solder, and Sn-Pb solder alloys are still widely used in today’s electronic packages. In this tudy, the interfacial reaction in the eutectic Sn-Ag and Sn-Pb solder joints was investigated with an assembly of a solder/Ni/Cu/Ti/Si3N4/Si multilayer structures. In the Sn-3.5Ag solder joints reflowed at 260°C, only the (Ni1-x,Cux)3Sn4 intermetallic compound (IMC) formed at the solder/Ni interface. For the Sn-37Pb solder reflowed at 225°C for one to ten cycles, only the (Ni1-x,Cux)3Sn4 IMC formed between the solder and the Ni/Cu under-bump metallization (UBM). Nevertheless, the (Cu1-y,Niy)6Sn5 IMC was observed in joints reflowed at 245°C after five cycles and at 265°C after three cycles. With the aid of microstructure evolution, quantitative analysis, and elemental distribution between the solder and Ni/Cu UBM, it was revealed that Cu content in the solder near the solder/IMC interface played an important role in the formation of the (Cu1-y,Niy)6Sn5 IMC. In addition, the diffusion behavior of Cu in eutectic Sn-Ag and Sn-Pb solders with the Ni/Cu UBM were probed and discussed. The atomic flux of Cu diffused through Ni was evaluated by detailed quantitative analysis in an electron probe microanalyzer (EPMA). During reflow, the atomic flux of Cu was on the order of 1016-1017 atoms/cm2sec in both the eutectic Sn-Ag and Sn-Pb systems.

  8. Influence of Silver nanoparticles addition on the phase transformation, mechanical properties and corrosion behaviour of Cu–Al–Ni shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Saud, Safaa N.; Hamzah, E., E-mail: esah@fkm.utm.my; Abubakar, T.; Bakhsheshi-Rad, H.R.; Farahany, S.; Abdolahi, A.; Taheri, M.M.

    2014-11-05

    Highlights: • Thermal analysis showed four different phase β, α, NiAl and γ2 during solidification. • The martensite appeared in the microstructure as a plate and needle like shape. • Shape recovery ratio of 80% was obtained after Ag nanoparticles addition. • Effect of Ag nanoparticles on the corrosion behaviour of Cu–Al–Ni SMA was investigated. - Abstract: Incorporation of silver nanoparticles into Cu-based shape memory alloys is recommended to enhance their phase transformation behaviour. However, this incorporation can affect their transformation temperatures, mechanical, microstructural and corrosion characteristics. Four different phase reactions β, α, NiAl and γ{sub 2} were detected on a derivative curve during the solidification by-computer-aided cooling curve thermal analysis. The highest fraction solid (82%) was calculated for the parent phase (β) based on the Newtonian baseline method. The microstructural changes and mechanical properties were investigated using field emission scanning electron microscopy, X-ray diffraction tensile test and shape memory effect test. It was found that the addition of Ag can control the phase morphology and orientations along with the formation of the Ag-rich precipitates, and thus the tensile strength, elongation, fracture stress–strain, yield strength and shape memory effect are improved. Remarkably, the shape recovery ratio reached approximately 80% of the original shape. The corrosion behaviour of the Cu–Al–Ni shape memory alloy were investigated using electrochemical tests in NaCl solution and their results showed that the corrosion potential (E{sub corr}) of Cu–Al–Ni SMA is shifted towards the nobler direction from −307.4 to −277.1 m V{sub SCE} with the addition of 0.25 wt.% Ag.

  9. Application of rapid solidification powder metallurgy processing to prepare Cu–Al–Ni high temperature shape memory alloy strips with high strength and high ductility

    Energy Technology Data Exchange (ETDEWEB)

    Vajpai, S.K., E-mail: vajpaisk@gmail.com [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India); Dube, R.K., E-mail: rkd@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India); Sangal, S., E-mail: sangals@iitk.ac.in [Department of Materials Science and Engineering, Indian Institute of Technology, Kanpur 208016, Uttar Pradesh (India)

    2013-05-15

    Cu–Al–Ni high temperature shape memory alloy (HTSMA) strips were successfully prepared from rapid solidified water atomized Cu–Al–Ni pre-alloyed powders via hot densification rolling of unsheathed sintered powder preforms. Finished heat-treated Cu–Al–Ni alloy strips had fine-grained structure, average grain size approximately 16 μm, and exhibited a combination of high strength and high ductility. It has been demonstrated that the redistribution of nano-sized alumina particles, present on the surface as well as inside the starting water atomized Cu–Al–Ni pre-alloyed powder particles, due to plastic deformation of starting powder particles during hot densification rolling resulted in the fine grained microstructure in the finished SMA strips. The finished SMA strips were almost fully martensitic in nature, consisting of a mixture of β{sub 1}{sup ′} and γ{sub 1}{sup ′} martensite. The average fracture strength and fracture strain of the finished SMA strips were 810 MPa and 12%, respectively, and the fractured specimens exhibited primarily micro-void coalescence type ductile nature of fracture. Finished Cu–Al–Ni SMA strips exhibited high characteristic transformation temperatures and an almost 100% one-way shape recovery was obtained in the specimens up to 4% applied deformation pre-strain. The retained two-way shape memory recovery increased with increasing applied training pre-strain, achieving a maximum value of 16.25% at 5% applied training pre-strain.

  10. Challenges and Progress in the Development of High-Temperature Shape Memory Alloys Based on NiTiX Compositions for High-Force Actuator Applications

    Science.gov (United States)

    Padula, Santo, II; Bigelow, Glen; Noebe, Ronald; Gaydosh, Darrell; Garg, Anita

    2006-01-01

    Interest in high-temperature shape memory alloys (HTSMA) has been growing in the aerospace, automotive, process control, and energy industries. However, actual materials development has seriously lagged component design, with current commercial NiTi alloys severely limited in their temperature capability. Additions of Pd, Pt, Au, Hf, and Zr at levels greater than 10 at.% have been shown to increase the transformation temperature of NiTi alloys, but with few exceptions, the shape memory behavior (strain recovery) of these NiTiX systems has been determined only under stress free conditions. Given the limited amount of basic mechanical test data and general lack of information regarding the work attributes of these materials, a program to investigate the mechanical behavior of potential HTSMAs, with transformation temperatures between 100 and 500 C, was initiated. This paper summarizes the results of studies, focusing on both the practical temperature limitations for ternary TiNiPd and TiNiPt systems based on the work output of these alloys and the ability of these alloys to undergo repeated thermal cycling under load without significant permanent deformation or "walking". These issues are ultimately controlled by the detwinning stress of the martensite and resistance to dislocation slip of the individual martensite and austenite phases. Finally, general rules that govern the development of useful, high work output, next-generation HTSMA materials, based on the lessons learned in this work, will be provided

  11. Steam reforming of cyclic model compounds of bio-oil over Ni-based catalysts: Product distribution and carbon formation

    DEFF Research Database (Denmark)

    Trane-Restrup, Rasmus; Jensen, Anker Degn

    2015-01-01

    Steam reforming (SR) and oxidative steam reforming (OSR) of furfural, 2-methylfuran, and guaiacol have been investigated in the temperature range 400-800°C at a steam to carbon (S/C)-ratio of 5 and oxygen to carbon (O/C)-ratio of 0.2-1.4 over Ni/CeO2-K/MgAl2O4. Carbon oxides and H2 were the major...... products in the SR of 2-methylfuran and furfural, while the by-products were methane, ethanol, 2-propanol, and acetone. Temperatures of 500°C or above were needed to minimize the formation of by-products in the SR of 2-methylfuran and furfural. Phenolics, like benzenediols and phenol, were produced in high...... yields in the SR of guaiacol and temperatures of 780°C were needed to totally convert guaiacol to carbon oxides and H2.Carbon deposition was observed in the SR of all three model compounds and was most severe for guaiacol followed by furfural and 2-methylfuran. The carbon deposition could be reduced...

  12. Characterization of a hot-rolled Cu--Al--Ni--Ti shape memory alloy

    International Nuclear Information System (INIS)

    Segui, C.; Pons, J.; Cesari, E.

    1999-01-01

    The changes in the martensitic transformation of a Cu-Al-Ni-Ti alloy hot-rolled at different temperatures have been studied in detail, covering different aspects such as ageing in the parent phase at temperatures ranging between 250 and 350 o C, stabilisation of the martensite and betatization of the previously hot-rolled specimens. Besides the evolution of transformation temperatures upon different thermal treatments, special attention has been paid to the changes in mechanical properties of the alloy, such as elastic modulus and internal friction. These results are analysed in relation to the microstructural changes as observed by transmission electron microscopy. (orig.)

  13. Annealing behavior and shape memory effect in NiTi alloy processed by equal-channel angular pressing at room temperature

    International Nuclear Information System (INIS)

    Shahmir, Hamed; Nili-Ahmadabadi, Mahmoud; Wang, Chuan Ting; Jung, Jai Myun; Kim, Hyoung Seop; Langdon, Terence G.

    2015-01-01

    A martensitic NiTi shape memory alloy was processed successfully by equal-channel angular pressing (ECAP) for one pass at room temperature using a core–sheath billet design. The annealing behavior and shape memory effect of the ECAP specimens were studied followed by post-deformation annealing (PDA) at 673 K for various times. The recrystallization and structural evolution during annealing were investigated by differential scanning calorimetry, dilatometry, X-ray diffraction, transmission electron microscopy and microhardness measurements. The results indicate that the shape memory effect improves by PDA after ECAP processing. Annealing for 10 min gives a good shape memory effect which leads to a maximum in recoverable strain of 6.9 pct upon heating where this is more than a 25 pct improvement compared with the initial state

  14. Torsional Properties of TiNi Shape Memory Alloy Tape for Rotary Actuator

    Science.gov (United States)

    Takeda, K.; Tobushi, H.; Mitsui, K.; Nishimura, Y.; Miyamoto, K.

    2012-12-01

    In order to develop novel shape memory actuators, the torsional deformation of a shape memory alloy (SMA) tape and the actuator models driven by the tape were investigated. The results obtained can be summarized as follows. In the SMA tape subjected to torsion, the martensitic transformation appears along both edges of the tape due to elongation of these elements and grows to the central part. The fatigue life in both the pulsating torsion and alternating torsion is expressed by the unified relationship of the dissipated work in each cycle. Based on an opening and closing door model and a solar-powered active blind model, the two-way rotary driving actuator with a small and simple mechanism can be developed by using torsion of the SMA tape.

  15. The Molecular Basis of Neural Memory. Part 7: Neural Intelligence (NI versus Artificial Intelligence (AI

    Directory of Open Access Journals (Sweden)

    Gerard Marx

    2017-07-01

    Full Text Available The link of memory to intelligence is incontestable, though the development of electronic artifacts with memory has confounded cognitive and computer scientists’ conception of memory and its relevance to “intelligence”. We propose two categories of “Intelligence”: (1 Logical (objective — mathematics, numbers, pattern recognition, games, programmable in binary format. (2 Emotive (subjective — sensations, feelings, perceptions, goals desires, sociability, sex, food, love. The 1st has been reduced to computational algorithms of which we are well versed, witness global technology and the internet. The 2nd relates to the mysterious process whereby (psychic emotive states are achieved by neural beings sensing, comprehending, remembering and dealing with their surroundings. Many theories and philosophies have been forwarded to rationalize this process, but as neuroscientists, we remain dissatisfied. Our own musings on universal neural memory, suggest a tripartite mechanism involving neurons interacting with their surroundings, notably the neural extracellular matrix (nECM with dopants [trace metals and neurotransmitters (NTs]. In particular, the NTs are the molecular encoders of emotive states. We have developed a chemographic representation of such a molecular code.To quote Longuet-Higgins, “Perhaps it is time for the term ‘artificial intelligence’ to be replaced by something more modest and less provisional”. We suggest “artifact intelligence” (ARTI or “machine intelligence” (MI, neither of which imply emulation of emotive neural processes, but simply refer to the ‘demotive’ (lacking emotive quality capability of electronic artifacts that employ a recall function, to calculate algorithms.

  16. Magnetic properties of Ni-Mn-Ga-Co-Cu tetragonal martensites exhibiting magnetic shape memory effect

    Czech Academy of Sciences Publication Activity Database

    Rameš, Michal; Heczko, Oleg; Sozinov, A.; Ullakko, K.; Straka, Ladislav

    2018-01-01

    Roč. 142, Jan (2018), s. 61-65 ISSN 1359-6462 R&D Projects: GA ČR GA16-00043S Institutional support: RVO:68378271 Keywords : ferromagnetic shape memory alloy * magnetic anisotropy * martensitic phase transformation * Heusler phases * twinning Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.747, year: 2016

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

    Czech Academy of Sciences Publication Activity Database

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

    2014-01-01

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

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

    International Nuclear Information System (INIS)

    Seward, K P

    1999-01-01

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

  19. Influence of the substitution of Ni for Fe on the microstructure evolution and magnetic phase transition in La(Fe1−xNix)11.5Si1.5 compounds

    International Nuclear Information System (INIS)

    Sun, Song; Ye, Rongchang; Long, Yi

    2013-01-01

    Graphical abstract: M–T curves show that all the compounds undergo a ferromagnetic–paramagnetic magnetic phase transition process. Besides, the Curie temperature T c of La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds increase monotonously from 195 K to 219 K when Ni content x varies from 0 to 0.03. Highlights: ► We substituted Fe by new element Ni in La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds. ► The microstructure evolution, magnetic phase transition and Curie temperature of La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds were investigated. ► The small substitution of Ni for Fe in La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds enhances the formation of 1:13 phase and helps the elimination of impurity phase significantly. ► The Curie temperature T C of La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds increase monotonously from 195 K to 219 K when x varies from 0 to 0.03. - Abstract: The influence of Ni substitution on the microstructure evolution and magnetic phase transition has been investigated in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds. Results show that partial substitution of Ni for Fe in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) alloys promotes fining of the as-cast microstructure. Besides, the formation of 1:13 phase and the elimination of impurity phases is facilitated significantly when annealed at 1373 K for 5 days. Large amounts of inhomogeneities are present in the annealed LaFe 11.5 Si 1.5 alloy. While almost single 1:13 phase is obtained in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0.02, 0.03) alloys. Moreover, the Curie temperature T C of La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds increase monotonously from 195 K to 219 K when Ni content x varies from 0 to 0.03.

  20. Characteristics and in vitro biological assessment of (Ti, O, N)/Ti composite coating formed on NiTi shape memory alloy

    International Nuclear Information System (INIS)

    Sun Tao; Wang Langping; Wang Min; Tong, Ho-Wang; Lu, William W.

    2011-01-01

    In this investigation, plasma immersion ion implantation and deposition (PIIID) was used to fabricate a (Ti, O, N)/Ti coating on NiTi shape memory alloy (SMA) to improve its long-term biocompatibility and wear resistance. The surface morphology, composition and roughness of uncoated and coated NiTi SMA samples were examined. Energy dispersive X-ray elemental mapping of cross-sections of (Ti, O, N)/Ti coated NiTi SMA revealed that Ni was depleted from the surface of coated samples. No Ni was detected by X-ray photoelectron spectroscopy on the surface of coated samples. Furthermore, three-point bending tests showed that the composite coating could undergo large deformation without cracking or delamination. After 1 day cell culture, SaOS-2 cells on coated samples spread better than those on uncoated NiTi SMA samples. The proliferation of SaOS-2 cells on coated samples was significantly higher at day 3 and day 7 of cell culture.

  1. Effects of water plasma immersion ion implantation on surface electrochemical behavior of NiTi shape memory alloys in simulated body fluids

    International Nuclear Information System (INIS)

    Liu, X.M.; Wu, S.L.; Chu, Paul K.; Chung, C.Y.; Chu, C.L.; Yeung, K.W.K.; Lu, W.W.; Cheung, K.M.C.; Luk, K.D.K.

    2007-01-01

    Water plasma immersion ion implantation (PIII) was conducted on orthopedic NiTi shape memory alloy to enhance the surface electrochemical characteristics. The surface composition of the NiTi alloy before and after H 2 O-PIII was determined by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) was utilized to determine the roughness and morphology of the NiTi samples. Potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) were carried out to investigate the surface electrochemical behavior of the control and H 2 O-PIII NiTi samples in simulated body fluids (SBF) at 37 deg. C as well as the mechanism. The H 2 O-PIII NiTi sample showed a higher breakdown potential (E b ) than the control sample. Based on the AFM results, two different physical models with related equivalent electrical circuits were obtained to fit the EIS data and explain the surface electrochemical behavior of NiTi in SBF. The simulation results demonstrate that the higher resistance of the oxide layer produced by H 2 O-PIII is primarily responsible for the improvement in the surface corrosion resistance

  2. Effect of surface modification by nitrogen ion implantation on the electrochemical and cellular behaviors of super-elastic NiTi shape memory alloy.

    Science.gov (United States)

    Maleki-Ghaleh, H; Khalil-Allafi, J; Sadeghpour-Motlagh, M; Shakeri, M S; Masoudfar, S; Farrokhi, A; Beygi Khosrowshahi, Y; Nadernezhad, A; Siadati, M H; Javidi, M; Shakiba, M; Aghaie, E

    2014-12-01

    The aim of this investigation was to enhance the biological behavior of NiTi shape memory alloy while preserving its super-elastic behavior in order to facilitate its compatibility for application in human body. The surfaces of NiTi samples were bombarded by three different nitrogen doses. Small-angle X-ray diffraction was employed for evaluating the generated phases on the bombarded surfaces. The electrochemical behaviors of the bare and surface-modified NiTi samples were studied in simulated body fluid (SBF) using electrochemical impedance and potentio-dynamic polarization tests. Ni ion release during a 2-month period of service in the SBF environment was evaluated using atomic absorption spectrometry. The cellular behavior of nitrogen-modified samples was studied using fibroblast cells. Furthermore, the effect of surface modification on super-elasticity was investigated by tensile test. The results showed the improvement of both corrosion and biological behaviors of the modified NiTi samples. However, no significant change in the super-elasticity was observed. Samples modified at 1.4E18 ion cm(-2) showed the highest corrosion resistance and the lowest Ni ion release.

  3. The effect of internal and external stress on two-way shape-memory behaviour in Co49Ni21.6Ga29.4 single crystals

    International Nuclear Information System (INIS)

    Liu, G D; Dai, X F; Luo, H Z; Liu, H Y; Meng, F B; Li, Y; Yu, X; Chen, J L; Wu, G H

    2011-01-01

    The effect of the internal stress on the two-way shape memory in Co 49 Ni 21.6 Ga 29.4 single crystals has been investigated. We found that the internal stress generated natively by the solidifying process works as a tensile force along the growth direction. Applying different compressive pre-stresses along the [0 0 1] direction, the shape-memory strain can be continuously changed from +1.0% to -2.3%. In the [1 1 0] direction, the strain monotonically increases from -2.0% to -4.0% due to a strong detwinning produced by the consistent effect of the external and internal stresses.

  4. Stress analysis, structure and magnetic properties of sputter deposited Ni-Mn-Ga ferromagnetic shape memory thin films

    Energy Technology Data Exchange (ETDEWEB)

    Annadurai, A. [Department of Physics, PSG College of Technology, Coimbatore 641004 (India); Manivel Raja, M., E-mail: mraja@dmrl.drdo.in [Defense Metallurgical Research Laboratory, Hyderabad 500058 (India); Prabahar, K.; Kumar, Atul [Defense Metallurgical Research Laboratory, Hyderabad 500058 (India); Kannan, M.D.; Jayakumar, S. [Department of Physics, PSG College of Technology, Coimbatore 641004 (India)

    2011-11-15

    The residual stress instituted in Ni-Mn-Ga thin films during deposition is a key parameter influencing their shape memory applications by affecting its structural and magnetic properties. A series of Ni-Mn-Ga thin films were prepared by dc magnetron sputtering on Si(1 0 0) and glass substrates at four different sputtering powers of 25, 45, 75 and 100 W for systematic investigation of the residual stress and its effect on structure and magnetic properties. The residual stresses in thin films were characterized by a laser scanning technique. The as-deposited films were annealed at 600 deg. C for 1 h in vacuum for structural and magnetic ordering. The compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. The annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. It was found that the increase of sputtering power induced coarsening in thin films. Typical saturation magnetization and coercivity values were found to be 330 emu/cm{sup 3} and 215 Oe, respectively. The films deposited at 75 and 100 W display both structural and magnetic transitions above room temperature. - Highlights: > Compressive stresses observed in as-deposited films transformed into tensile stresses upon annealing. > Annealed films were found to be crystalline and possess mixed phases of both austenite and martensite, exhibiting good soft magnetic properties. > The highest Curie transition in the films was observed at 365 K. > The films deposited at 75 and 100 W display both structural and magnetic transitions above room temperature.

  5. Shape memory characteristics and mechanical properties of powder metallurgy processed Ti50Ni40Cu10 alloy.

    Science.gov (United States)

    Kim, Yeon-Wook

    2014-10-01

    Ti-Ni-Cu alloy powders were prepared by gas atomization and porous bulk specimens were fabricated by spark plasma sintering (SPS). The microstructure of as-solidified powders exhibited a cellular structure and they contained a high density of nano-sized porosities which were located in the intercellular regions. XRD analysis showed that one-step martensitic transformation of B2-B19 occurred in all alloy powders and SPS specimens. When the martensitic transformation start temperature (M(s)) and austenite transformation finish temperature (A(f)) were determined in order to analyze the dependence of powder size on transformation temperatures, the M(s) increased slightly from -17.5 degrees C to - 14.6 degrees C as increasing the powder size ranging from between 25 and 50 μm to ranging between 100 and 150 μm. However, the M(s) and A(f) of the as-atomized powders is much smaller than those of SPS specimens and the M(s) of porous specimen was about 10.9 degrees C. Loading-unloading compressive tests were carried out to investigate the mechanical properties of porous Ti-Ni-Cu specimen. The specimen was compressed to the strain of 6% at a temperature higher than A,. After unloading, the residual strain was 2.1%. After the compressed specimen was heated to 60 degrees C and held for 30 minutes and then cooled to room temperature, the changes in the length of the specimens were measured. Then it was found that the recovered strain ascribed to shape memory effect was 1.5%.

  6. Micro-processing of NiMnGa shape memory alloy by using a nanosecond fiber laser

    Science.gov (United States)

    Biffi, C. A.; Tuissi, A.

    2016-04-01

    The interest on Ferromagnetic Shape Memory Alloys (FSMAs), such as NiMnGa, is growing up, thanks to their functional properties to be employed in a new class of micro-devices. The most evident critical issue, limiting the use of these systems in the production of industrial devices, is the brittleness of the bulk material; its workability by using convectional processing methods is very limited. Thus, alternative processing methods, including laser processing, are encouraged for the manufacture of FSMAs based new devices. In this work, the effect of the nanosecond laser microprocessing on Ni45Mn33Ga22 [at%] has been studied. Linear grooves were realized by a nanosecond 30 W fiber laser; the machined surfaces were analyzed with scanning electron microscopy, coupled with energetic dispersion spectroscopy for the composition analysis. The morphology of the grooves was affected by the laser scanning velocity and the number of laser pulses while the measured material removal rate appeared to be influenced mainly by the number of laser pulses. Compositional modification, associated to the loss of Ga content, was detected only for the lower scanning velocity, because of the high fluence. On the contrary, by increasing the velocity up to 1000 mm/s no Ga loss can be seen, making possible the laser processing of this functional alloy without its chemical modification. The use of short pulses allowed also to reduce the amount of recast material and the compositional change with respect to long pulses. Finally, the calorimetric analysis indicated that laser nanosecond microprocessing could affect the functional properties of this alloy: a larger decrease of the characteristic temperatures of the martensitic transformation was observed in correspondence of the low scanning velocity.

  7. 161Dy Moessbauer spectroscopy of the intermetallic compounds DyNi2Si2, DyNi2Ge2 and DyAg2Si2

    International Nuclear Information System (INIS)

    Onodera, Hideya; Murata, Akifumi; Koizuka, Masaaki; Ohashi, Masayoshi; Yamaguchi, Yasuo

    1994-01-01

    161 Dy Moessbauer spectroscopic study has been performed on DyNi 2 Si 2 , DyNi 2 Ge 2 and DyAg 2 Si 2 in order to clarify microscopic properties of antiferromagnets with incommensurate and sinusoidally moment-modulated structure. The experiments were done using the standard 161 Tb Moessbauer sources prepared by neutron irradiation at the Japan Material Testing Reactor. The Moessbauer spectra of DyNi 2 Si 2 are analyzed satisfactorily by a single set of hyperfine parameters, and hence the sinusoidal moment-modulation is considered to be realized through a distribution of spin relaxation rate. The broadened spectra of DyNi 2 Ge 2 are fitted tentatively by three subspectra. It seems for DyNi 2 Ge 2 that the incommensurate arrangement of Dy moments differed in magnitude as well as the distribution of spin relaxation rate originates the moment modulation. The fact that the spectrum of DyAg 2 Si 2 at 3 K consists of two distinct subspectra ensures the complicated antiferromagnetic structure where two kinds of Dy moments differed in magnitude are arranged noncollinearly. (author)

  8. Thermomechanical behavior and microstructural evolution of a Ni(Pd)-rich Ni{sub 24.3}Ti{sub 49.7}Pd{sub 26} high temperature shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Benafan, O., E-mail: othmane.benafan@nasa.gov [NASA Glenn Research Center, Structures and Materials Division, Cleveland, OH 44135 (United States); Garg, A. [University of Toledo, Toledo, OH 43606 (United States); NASA Glenn Research Center, Structures and Materials Division, Cleveland, OH 44135 (United States); Noebe, R.D.; Bigelow, G.S.; Padula, S.A. [NASA Glenn Research Center, Structures and Materials Division, Cleveland, OH 44135 (United States); Gaydosh, D.J. [Ohio Aerospace Institute, Cleveland, OH 44142 (United States); NASA Glenn Research Center, Structures and Materials Division, Cleveland, OH 44135 (United States); Vaidyanathan, R. [Advanced Materials Processing and Analysis Center, Materials Science and Engineering Department, University of Central Florida, Orlando, FL 32816 (United States); Clausen, B.; Vogel, S.C. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

    2015-09-15

    Highlights: • A Ni(Pd)-rich Ni{sub 24.3}Ti{sub 49.7}Pd{sub 26} high temperature shape memory alloy was characterized. • Aging resulted in fine dispersion of nano-sized precipitates. • Thermomechanical cycling resulted in dimensional instabilities due to lattice defects. • A two-way shape memory effect strain of 2% strain was obtained after cycling. - Abstract: The effect of thermomechanical cycling on a slightly Ni(Pd)-rich Ni{sub 24.3}Ti{sub 49.7}Pd{sub 26} (near stochiometric Ni–Ti basis with Pd replacing Ni) high temperature shape memory alloy was investigated. Aged tensile specimens (400 °C/24 h/furnace cooled) were subjected to constant-stress thermal cycling in conjunction with microstructural assessment via in situ neutron diffraction and transmission electron microscopy (TEM), before and after testing. It was shown that in spite of the slightly Ni(Pd)-rich composition and heat treatment used to precipitation harden the alloy, the material exhibited dimensional instabilities with residual strain accumulation reaching 1.5% over 10 thermomechanical cycles. This was attributed to insufficient strengthening of the material (insufficient volume fraction of precipitate phase) to prevent plasticity from occurring concomitant with the martensitic transformation. In situ neutron diffraction revealed the presence of retained martensite while cycling under 300 MPa stress, which was also confirmed by transmission electron microscopy of post-cycled samples. Neutron diffraction analysis of the post-thermally-cycled samples under no-load revealed residual lattice strains in the martensite and austenite phases, remnant texture in the martensite phase, and peak broadening of the austenite phase. Texture developed in the martensite phase was composed mainly of those martensitic tensile variants observed during thermomechanical cycling. Presence of a high density of dislocations, deformation twins, and retained martensite was revealed in the austenite state via in

  9. Development of Ni-Based Catalysts Derived from Hydrotalcite-Like Compounds Precursors for Synthesis Gas Production via Methane or Ethanol Reforming

    OpenAIRE

    Ya-Li Du; Xu Wu; Qiang Cheng; Yan-Li Huang; Wei Huang

    2017-01-01

    As a favorably clean fuel, syngas (synthesis gas) production has been the focus of concern in past decades. Substantial literatures reported the syngas production by various catalytic reforming reactions particularly in methane or ethanol reforming. Among the developed catalysts in these reforming processes, Ni-based catalysts from hydrotalcite-like compounds (HTLcs) precursors have drawn considerable attention for their preferable structural traits. This review covers the recent literature r...

  10. The study of new complex compounds of Ni (II) and Co (II) with N- hydroxy-succinimide and their potential applications as sensors

    Science.gov (United States)

    Sibiescu, Doina; Tutulea, Mihaela-Dana; Mîţă, Carmen; Stan, Corneliu; Roţca, Ioan; Vizitiu, Mihaela

    2010-11-01

    In this paper, the study of obtaining new coordination compounds of Ni (II) and Co(II) using as ligand, N-hydroxy-succinimide, was presented. Also, the stability constants of these compounds in aqueous medium were determined. The obtaining conditions and the stability of the new compounds were accomplished in aqueous solutions using characteristic methods for coordination compounds: pH-metry, conductometry and UV-VIS absorption spectroscopy. The combination ratios and the stability constants were determined with methods characteristic for studies in solutions. From experimental data resulted that the combination ratio of central metallic atoms with the ligand N-hydroxy-succinimide was: 1:1 and respectively 1:2. In the experiments were used salts of NiCl2.6H2O and CoCl2.6H2O. The optimal domain of pH stability of the studied compounds is limited between 5.74 - 5.86 for Co- N-hydroxy-succinimide (for molar ratio 1:1 and 1:2) and respectively 5.69 - 5.87 for Ni-N-hydroxysuccinimide( for molar ratio 1:1 and 1:2, too). It is important to mention that these compounds were used with very good results in determination of wastewaters from textile, metallurgical, chemical and food industry. Complexion reactions with this ligand are very sensitive for the cations in this paper mentioned. Therefore it is used most often with success in analytical chemistry and also it is posibil to use as sensors. The new complex compounds has electronics transitions at λ = 517 nm for both complexes Co-N-hydroxy-succinimide at molar ratio 1:1 and 1:2 and also at the same λ = 397nm for Ni-N-hydroxysuccinimide at molar ratio 1:1 and 1:2. These complexes compounds was separated and recrystallized from aqueous solution. From the spectrophotometric data it was determined the type and the nature of the electronics transitions by Dq parameters.

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  12. Internal friction of Ti-Ni-Cu ternary shape memory alloys

    International Nuclear Information System (INIS)

    Yoshida, I.; Monma, D.; Iino, K.; Ono, T.; Otsuka, K.; Asai, M.

    2004-01-01

    Low frequency internal friction was measured on three specimens of Ti-Ni-Cu ternary alloys, the Cu content varying from 10 to 20 at.%, while Ti content was fixed at 50 at.%. The internal friction spectrum consists mainly of two peaks, a sharper one associated with the B2-B19 transformation and the other one at around 250 K, which is much broader and higher than the former. The peak height of the latter is 0.2 for the specimen containing 20% Cu, which shows that this alloy can be an excellent high damping material. Transformation behavior was studied by electrical resistivity, thermopower and DSC measurements, and was compared with the result of internal friction measurements. Solution treatment at higher temperatures lowers the internal friction peak markedly. Scanning electron microscopy observation reveals that the behaviors of precipitates are different for different solution treatment temperature, suggesting that the precipitation behavior is crucial in the damping properties

  13. Nanoscale mechanical surface properties of single crystalline martensitic Ni-Mn-Ga ferromagnetic shape memory alloys

    International Nuclear Information System (INIS)

    Jakob, A M; Müller, M; Rauschenbach, B; Mayr, S G

    2012-01-01

    Located beyond the resolution limit of nanoindentation, contact resonance atomic force microscopy (CR-AFM) is employed for nano-mechanical surface characterization of single crystalline 14M modulated martensitic Ni-Mn-Ga (NMG) thin films grown by magnetron sputter deposition on (001) MgO substrates. Comparing experimental indentation moduli-obtained with CR-AFM-with theoretical predictions based on density functional theory (DFT) indicates the central role of pseudo plasticity and inter-martensitic phase transitions. Spatially highly resolved mechanical imaging enables the visualization of twin boundaries and allows for the assessment of their impact on mechanical behavior at the nanoscale. The CR-AFM technique is also briefly reviewed. Its advantages and drawbacks are carefully addressed. (paper)

  14. Structure and microstructure of Ni-Mn-Ga single crystal exhibiting magnetic shape memory effect analysed by high resolution X-ray diffraction

    Czech Academy of Sciences Publication Activity Database

    Heczko, Oleg; Cejpek, P.; Drahokoupil, Jan; Holý, V.

    2016-01-01

    Roč. 115, Aug (2016), s. 250-258 ISSN 1359-6454 R&D Projects: GA ČR GA13-30397S; GA ČR GA15-00262S Institutional support: RVO:68378271 Keywords : magnetic field-induced strain * magnetic shape memory effect * X-ray diffraction * structure of Ni-Mn-Ga Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.301, year: 2016

  15. Stress-induced martensitic transformations in a Cu-Al-Ni shape memory alloy studied by in situ transmission electron microscopy

    Czech Academy of Sciences Publication Activity Database

    Zárubová, Niva; Gemperlová, Juliana; Gärtnerová, Viera; Gemperle, Antonín

    481-482, č. 5 (2008), s. 457-461 ISSN 0921-5093 R&D Projects: GA ČR GA202/04/2016; GA AV ČR(CZ) IAA200100627 Institutional research plan: CEZ:AV0Z10100520 Keywords : in situ TEM straining * CuAlNi shape memory alloy * stress -induced formation of martensite Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.806, year: 2008

  16. Ellipsometry applied to phase transitions and relaxation phenomena in Ni.sub.2./sub.MnGa ferromagnetic shape memory alloy

    Czech Academy of Sciences Publication Activity Database

    Dejneka, Alexandr; Zablotskyy, Vitaliy A.; Tyunina, Marina; Jastrabík, Lubomír; Pérez-Landazábal, J.I.; Recarte, V.; Sánchez-Alarcos, V.; Chernenko, V.A.

    2012-01-01

    Roč. 101, č. 14 (2012), "141908-1"-"141908-5" ISSN 0003-6951 R&D Projects: GA TA ČR TA01010517; GA ČR GAP108/12/1941 Institutional research plan: CEZ:AV0Z10100522 Keywords : shape memory alloy * ellipsometry * Ni 2 MnGa Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.794, year: 2012 http://dx.doi.org/10.1063/1.4757393

  17. Long-Range Atomic Order and Entropy Change at the Martensitic Transformation in a Ni-Mn-In-Co Metamagnetic Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Vicente Sánchez-Alarcos

    2014-05-01

    Full Text Available The influence of the atomic order on the martensitic transformation entropy change has been studied in a Ni-Mn-In-Co metamagnetic shape memory alloy through the evolution of the transformation temperatures under high-temperature quenching and post-quench annealing thermal treatments. It is confirmed that the entropy change evolves as a consequence of the variations on the degree of L21 atomic order brought by thermal treatments, though, contrary to what occurs in ternary Ni-Mn-In, post-quench aging appears to be the most effective way to modify the transformation entropy in Ni-Mn-In-Co. It is also shown that any entropy change value between around 40 and 5 J/kgK can be achieved in a controllable way for a single alloy under the appropriate aging treatment, thus bringing out the possibility of properly tune the magnetocaloric effect.

  18. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-08-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of Dc = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times.

  19. Damage-based life prediction model for uniaxial low-cycle stress fatigue of super-elastic NiTi shape memory alloy microtubes

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-01-01

    Based on the experimental observations for the uniaxial low-cycle stress fatigue failure of super-elastic NiTi shape memory alloy microtubes (Song et al 2015 Smart Mater. Struct. 24 075004) and a new definition of damage variable corresponding to the variation of accumulated dissipation energy, a phenomenological damage model is proposed to describe the damage evolution of the NiTi microtubes during cyclic loading. Then, with a failure criterion of D c = 1, the fatigue lives of the NiTi microtubes are predicted by the damage-based model, the predicted lives are in good agreement with the experimental ones, and all of the points are located within an error band of 1.5 times. (paper)

  20. The Naturally Occurring Compound Garcinia Indica Selectively Impairs the Reconsolidation of a Cocaine-Associated Memory

    OpenAIRE

    Monsey, Melissa S; Sanchez, Hayde; Taylor, Jane R

    2016-01-01

    Sustained abstinence from cocaine use is frequently compromised by exposure to environmental stimuli that have previously been strongly associated with drug taking. Such cues trigger memories of the effects of the drug, leading to craving and potential relapse. Our work has demonstrated that manipulating cocaine-cue memories by destabilizing them through interfering with the reconsolidation process is one potential therapeutic tool by which to prolong abstinence. Here, we examine the use of t...

  1. Non-volatile memory devices with redox-active diruthenium molecular compound

    International Nuclear Information System (INIS)

    Pookpanratana, S; Zhu, H; Bittle, E G; Richter, C A; Li, Q; Hacker, C A; Natoli, S N; Ren, T

    2016-01-01

    Reduction-oxidation (redox) active molecules hold potential for memory devices due to their many unique properties. We report the use of a novel diruthenium-based redox molecule incorporated into a non-volatile Flash-based memory device architecture. The memory capacitor device structure consists of a Pd/Al 2 O 3 /molecule/SiO 2 /Si structure. The bulky ruthenium redox molecule is attached to the surface by using a ‘click’ reaction and the monolayer structure is characterized by x-ray photoelectron spectroscopy to verify the Ru attachment and molecular density. The ‘click’ reaction is particularly advantageous for memory applications because of (1) ease of chemical design and synthesis, and (2) provides an additional spatial barrier between the oxide/silicon to the diruthenium molecule. Ultraviolet photoelectron spectroscopy data identified the energy of the electronic levels of the surface before and after surface modification. The molecular memory devices display an unsaturated charge storage window attributed to the intrinsic properties of the redox-active molecule. Our findings demonstrate the strengths and challenges with integrating molecular layers within solid-state devices, which will influence the future design of molecular memory devices. (paper)

  2. Characterization of the shape memory properties of a Ni45.3Ti39.7Hf10Pd5 alloy

    International Nuclear Information System (INIS)

    Acar, E.; Karaca, H.E.; Tobe, H.; Noebe, R.D.; Chumlyakov, Y.I.

    2013-01-01

    Highlights: •Ni 45.3 Ti 39.7 Hf 10 Pd 5 alloys have transformation strain of up to 4.6% and work output of up to 29 J cm −3 . •The alloy showed good superelastic behavior at 90 °C with recoverable strain of 4.3%. •The alloy exhibited 1.6% two-way shape memory strain after a simple training procedure. •The formation of 〈0 1 1〉 type II twins in martensite plates results in large transformation strain. -- Abstract: The load-biased shape memory and superelastic responses of a Ni 45.3 Ti 39.7 Hf 10 Pd 5 polycrystalline alloy were investigated in compression. Transformation strain of up to 4.6% and work output of up to 29 J cm −3 were determined from load-biased thermal cycling experiments. The alloy showed good superelastic behavior at 90 o C with recoverable strain of over 4%. It was also determined that the Ni 45.3 Ti 39.7 Hf 10 Pd 5 alloy could develop two-way shape memory strain of 1.6% without an intense training process. Transmission electron microscopy (TEM) revealed that the internal twins formed in the martensite variants were 〈0 1 1〉 type II twins

  3. Pt Single Atoms Embedded in the Surface of Ni Nanocrystals as Highly Active Catalysts for Selective Hydrogenation of Nitro Compounds.

    Science.gov (United States)

    Peng, Yuhan; Geng, Zhigang; Zhao, Songtao; Wang, Liangbing; Li, Hongliang; Wang, Xu; Zheng, Xusheng; Zhu, Junfa; Li, Zhenyu; Si, Rui; Zeng, Jie

    2018-06-13

    Single-atom catalysts exhibit high selectivity in hydrogenation due to their isolated active sites, which ensure uniform adsorption configurations of substrate molecules. Compared with the achievement in catalytic selectivity, there is still a long way to go in exploiting the catalytic activity of single-atom catalysts. Herein, we developed highly active and selective catalysts in selective hydrogenation by embedding Pt single atoms in the surface of Ni nanocrystals (denoted as Pt 1 /Ni nanocrystals). During the hydrogenation of 3-nitrostyrene, the TOF numbers based on surface Pt atoms of Pt 1 /Ni nanocrystals reached ∼1800 h -1 under 3 atm of H 2 at 40 °C, much higher than that of Pt single atoms supported on active carbon, TiO 2 , SiO 2 , and ZSM-5. Mechanistic studies reveal that the remarkable activity of Pt 1 /Ni nanocrystals derived from sufficient hydrogen supply because of spontaneous dissociation of H 2 on both Pt and Ni atoms as well as facile diffusion of H atoms on Pt 1 /Ni nanocrystals. Moreover, the ensemble composed of the Pt single atom and nearby Ni atoms in Pt 1 /Ni nanocrystals leads to the adsorption configuration of 3-nitrostyrene favorable for the activation of nitro groups, accounting for the high selectivity for 3-vinylaniline.

  4. Phase Transformation and Creep Behavior in Ti50Pd30Ni20 High Temperature Shape Memory Alloy in Compression

    Science.gov (United States)

    Kumar, Parikshith K.; Desai, Uri; Monroe, James; Lagoudas, Dimitris C.; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glenn

    2010-01-01

    The creep behavior and the phase transformation of Ti50Pd30Ni20 High Temperature Shape Memory Alloy (HTSMA) is investigated by standard creep tests and thermomechanical tests. Ingots of the alloy are induction melted, extruded at high temperature, from which cylindrical specimens are cut and surface polished. A custom high temperature test setup is assembled to conduct the thermomechanical tests. Following preliminary monotonic tests, standard creep tests and thermally induced phase transformation tests are conducted on the specimen. The creep test results suggest that over the operating temperatures and stresses of this alloy, the microstructural mechanisms responsible for creep change. At lower stresses and temperatures, the primary creep mechanism is a mixture of dislocation glide and dislocation creep. As the stress and temperature increase, the mechanism shifts to predominantly dislocation creep. If the operational stress or temperature is raised even further, the mechanism shifts to diffusion creep. The thermally induced phase transformation tests show that actuator performance can be affected by rate independent irrecoverable strain (transformation induced plasticity + retained martensite) as well as creep. The rate of heating and cooling can adversely impact the actuators performance. While the rate independent irrecoverable strain is readily apparent early in the actuators life, viscoplastic strain continues to accumulate over the lifespan of the HTSMA. Thus, in order to get full actuation out of the HTSMA, the heating and cooling rates must be sufficiently high enough to avoid creep.

  5. Influence of the addition of chromium in the microstructure and property of Cu-Al-Ni shape memory alloy

    International Nuclear Information System (INIS)

    Teixeira, C.A.; Coelho, R.E.; Lima, P.C. de; Carvalho, C.O. de; Conrado, L.C.

    2016-01-01

    The Copper based alloys with addition of a fourth element have been studied for 20 years. These alloys, depending on their composition present shape memory effect structure and now a day possess a diversity of applications. Considering the importance of these materials, it was developed in this research alloys of Cu-Al-Ni with addition of Cr in different percentages (0.2, 0.4, 0.7 and 2.26wt.%). A plasma furnace (Company-EDG, model-Discovery), with vacuum control and argon gas injection, was utilized. Posteriorly, the samples underwent heat treatment of solubilization. This treatment consisted in submitting all samples to a temperature of 900 deg C for 1 hour and followed by water solution (salt, water, ice and alcohol) quenching at a temperature of -10 deg C. The samples were polished and etched with Ferric Chloride. All samples were analyzed X-ray Fluorescence, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). XRD was carried out with a tension 30kV from 25 deg to 100 deg. It was possible to verify, through the obtained SEM images, that Cr has a fundamental role in the martensite structure evolution and with XRD analyses it was observed that with the increase of Cr, results in the formation of phases 18R and 2H with a decrease of phase γ2, the last one unwanted to this type of alloy. (author)

  6. Martensitic transformation in a high textured Cu-Al-Ni shape memory alloy

    International Nuclear Information System (INIS)

    Sobrero, C; Roatta, A; Malarria, J; Bolmaro, R.

    2008-01-01

    The formation of the 18R1 martensite in copper based shape memory alloys occurs spontaneously during cooling by the localized formation of four self-accommodating variants in a plate group. Each of the six plate groups have four self-accommodating variants, resulting on twenty four transformation variants from de parent phase (β 1 ) to the martensitic one (β 1 '). In the current work experimental texture measurements for both phases and simulations have been carried out to establish the effect of the different activated variants in the transformation texture. The high temperature textures were measured with an on purpose designed stage and the samples were cycled a few times to evaluate texture degradation

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  8. Phase stabilities of pyrite-related MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te): A systematic DFT study

    International Nuclear Information System (INIS)

    Bachhuber, Frederik; Krach, Alexander; Furtner, Andrea; Söhnel, Tilo; Peter, Philipp; Rothballer, Jan; Weihrich, Richard

    2015-01-01

    Pyrite-type and related systems appear for a wide range of binary and ternary combinations of transition metals and main group elements that form Zintl type dumbbell anion units. Those representatives with 20 valence electrons exhibit an extraordinary structural flexibility and interesting properties as low-gap semiconductors or thermoelectric and electrode materials. This work is devoted to the systematic exploration of novel compounds within the class of MTCh compounds (M=Ni, Pd, Pt; T=Si, Ge, Sn, Pb; Ch=S, Se, Te) by means of density functional calculations. Their preferred structures are predicted from an extended scheme of colored pyrites and marcasites. To determine their stabilities, competing binary MT 2 and MCh 2 boundary phases are taken into account as well as ternary M 3 T 2 Ch 2 and M 2 T 3 Ch 3 systems. Recently established stability diagrams are presented to account for MTCh ordering phenomena with a focus on a not-yet-reported ordering variant of the NiAs 2 type. Due to the good agreement with experimental data available for several PtTCh systems, the predictions for the residual systems are considered sufficiently accurate. - Graphical abstract: Compositional and structural stability of MTCh compounds is investigated from first principle calculations. A conceptional approach is presented to study and predict novel stable and metastable compounds and structures of low gap semiconductors with TCh dumbbell units that are isoelectronic and structurally related to pyrite (FeS 2 ). - Highlights: • Study of compositional stability of MTCh vs. M 3 T 2 Ch 2 and M 2 T 3 Ch 3 compounds. • Study of structural stability of known and novel MTCh compounds. • Prediction of novel stable and metastable structures and compounds isoelectronic to pyrite, FeS 2

  9. Magnetic properties and magnetocaloric effect in the HoNi1−xCuxIn (x=0, 0.1, 0.3, 0.4) intermetallic compounds

    International Nuclear Information System (INIS)

    Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Tang, Cheng-Chun; He, Xiao-Nan; Zheng, Xinqi; Wu, Jian-Feng; Sun, Ji-Rong; Shen, Bao-Gen

    2014-01-01

    The magnetic properties and magnetocaloric effect (MCE) in HoNi 1−x Cu x In (x=0, 0.1, 0.3, 0.4) compounds have been investigated. With the substitution of Cu for Ni, the Ho magnetic moment will cant from the c-axis, and form a complicated magnetic structure. These compounds exhibit two successive magnetic transitions with the increase in temperature. The large reversible magnetocaloric effects have been observed in HoNi 1−x Cu x In compounds around T ord , with no thermal and magnetic hysteresis loss. The large reversible isothermal magnetic entropy change (−ΔS M ) is 20.2 J/kg K and the refrigeration capacity (RC) reaches 356.7 J/kg for field changes of 5 T for HoNi 0.7 Cu 0.3 In. Especially, the value of −ΔS M (12.5 J/kg K) and the large RC (132 J/kg) are observed for field changes of 2 T for HoNi 0.9 Cu 0.1 In. Additionally, the values of RC are improved to 149 J/K for the field changes of 2 T due to a wide temperature span for the mix of HoNi 0.9 Cu 0.1 In and HoNi 0.7 Cu 0.3 In compounds with the mass ratio of 1:1. These compounds with excellent MCE are expected to have effective applications in magnetic refrigeration around 20 K. - Highlights: • For magnetic-field changes of 2 T, the values of RC are improved to 149 J/K. • MCEs of these compounds show no thermal and magnetic hysteresis. • Compounds show two successive magnetic transitions with the increase in temperature. • With the substitution of Cu for Ni, compounds form a complicated magnetic structure

  10. Catalytic Steam Reforming of Toluene as a Model Compound of Biomass Gasification Tar Using Ni-CeO2/SBA-15 Catalysts

    Directory of Open Access Journals (Sweden)

    Erik Dahlquist

    2013-07-01

    Full Text Available Nickel supported on SBA-15 doped with CeO2 catalysts (Ni-CeO2/SBA-15 was prepared, and used for steam reforming of toluene which was selected as a model compound of biomass gasification tar. A fixed-bed lab-scale set was designed and employed to evaluate the catalytic performances of the Ni-CeO2/SBA-15 catalysts. Experiments were performed to reveal the effects of several factors on the toluene conversion and product gas composition, including the reaction temperature, steam/carbon (S/C ratio, and CeO2 loading content. Moreover, the catalysts were subjected to analysis of their carbon contents after the steam reforming experiments, as well as to test the catalytic stability over a long experimental period. The results indicated that the Ni-CeO2/SBA-15 catalysts exhibited promising capabilities on the toluene conversion, anti-coke deposition and catalytic stability. The toluene conversion reached as high as 98.9% at steam reforming temperature of 850 °C and S/C ratio of 3 using the Ni-CeO2(3wt%/SBA-15 catalyst. Negligible coke formation was detected on the used catalyst. The gaseous products mainly consisted of H2 and CO, together with a little CO2 and CH4.

  11. Simulation of the precipitation process of ordered intermetallic compounds in binary and ternary Ni-Al-based alloys by the phase-field model

    International Nuclear Information System (INIS)

    Hou Hua; Zhao Yuhong; Zhao Yuhui

    2009-01-01

    With the microscopic phase-field model, atomic-scale computer simulation programs for the precipitation mechanism of the ordered intermetallic compound γ' in binary Ni-15.5 at.%Al alloy, θ and γ' in ternary Ni 75 Al x V 25-x alloys were worked out based on the microscopic diffusion equation and non-equilibrium free energy. The simulation can be applied to the whole precipitation process and composition range. A prior assumptions on the new phase structure or transformation path was unnecessary, the possible non-equilibrium phases, atomic clustering and ordering could be described automatically, and atomic images, order parameters and volume fractions of precipitates were obtained. Computer simulation was performed systematically on the precipitation mechanism, precipitation sequence of θ and γ' in complicated system with ordering and clustering simultaneously. Through the simulated atomic images and chemical order parameters of precipitates, we can explain the complex precipitation mechanisms of θ (Ni 3 V) and γ' (Ni 3 Al) ordered phases. For the binary alloy, the precipitation mechanism of γ' phase has the characteristic of both non-classical nucleation and growth (NCNG) and congruent ordering and spinodal decomposition (COSD). For the ternary alloys, the precipitation characteristic of γ' phase transforms from NCNG to COSD gradually, otherwise, the precipitation characteristic of θ phase transforms from COSD to NCNG mechanism gradually

  12. Irreversibility in room temperature current–voltage characteristics of NiFe{sub 2}O{sub 4} nanoparticles: A signature of electrical memory effect

    Energy Technology Data Exchange (ETDEWEB)

    Dey, P., E-mail: pujaiitkgp2007@gmail.com [Department of Physics, Kazi Nazrul University, Asansol, W.B. 713340 (India); Debnath, Rajesh; Singh, Swati; Mandal, S.K. [Department of Physics, National Institute of Technology Agartala, Tripura 799046 (India); Roy, J.N. [Department of Physics, Kazi Nazrul University, Asansol, W.B. 713340 (India); Department of Physics, National Institute of Technology Agartala, Tripura 799046 (India)

    2017-01-01

    Room temperature I–V characteristics study, both in presence and absence of magnetic field (1800 Oe), has been performed on NiFe{sub 2}O{sub 4} nanoparticles, having different particle size (φ~14, 21 and 31 nm). Our experiments on these nanoparticles provide evidences for: (1) electrical irreversibility or hysteretic behaviour; (2) positive magnetoresistance and (3) magnetic field dependent electrical irreversibility or hysteresis in the sample. “Hysteretic” nature of I–V curve reveals the existence of electrical memory effect in the sample. Significantly, such hysteresis has been found to be tuned by magnetic field. In order to explain the observed electrical irreversibility, we have proposed a phenomenological model on the light of induced polarization in the sample. Both the positive magnetoresistance and the observed magnetic field dependence of electrical irreversibility have been explained through magnetostriction phenomenon. Interestingly, such effects are found to get reduced with increasing particle size. For NiFe{sub 2}O{sub 4} nanoparticles having φ=31 nm, we did not observe any irreversibility effect. This feature has been attributed to the enhanced grain surface effect that in turn gives rise to the residual polarization and hence electrical memory effect in NiFe{sub 2}O{sub 4} nanoparticles, having small nanoscopic particle size. - Highlights: • I-V characteristics study of NiFe{sub 2}O{sub 4} nanoparticles with varying particle sizes. • Experiments evident electrical hysteretic behaviour, i.e., electrical memory effect. • Magnetic field dependent electrical irreversibility is due to magnetostriction. • A phenomenological model has been proposed on the light of induced polarization. • Such electrical irreversibility decreases with increasing particle sizes.

  13. Irreversibility in room temperature current–voltage characteristics of NiFe_2O_4 nanoparticles: A signature of electrical memory effect

    International Nuclear Information System (INIS)

    Dey, P.; Debnath, Rajesh; Singh, Swati; Mandal, S.K.; Roy, J.N.

    2017-01-01

    Room temperature I–V characteristics study, both in presence and absence of magnetic field (1800 Oe), has been performed on NiFe_2O_4 nanoparticles, having different particle size (φ~14, 21 and 31 nm). Our experiments on these nanoparticles provide evidences for: (1) electrical irreversibility or hysteretic behaviour; (2) positive magnetoresistance and (3) magnetic field dependent electrical irreversibility or hysteresis in the sample. “Hysteretic” nature of I–V curve reveals the existence of electrical memory effect in the sample. Significantly, such hysteresis has been found to be tuned by magnetic field. In order to explain the observed electrical irreversibility, we have proposed a phenomenological model on the light of induced polarization in the sample. Both the positive magnetoresistance and the observed magnetic field dependence of electrical irreversibility have been explained through magnetostriction phenomenon. Interestingly, such effects are found to get reduced with increasing particle size. For NiFe_2O_4 nanoparticles having φ=31 nm, we did not observe any irreversibility effect. This feature has been attributed to the enhanced grain surface effect that in turn gives rise to the residual polarization and hence electrical memory effect in NiFe_2O_4 nanoparticles, having small nanoscopic particle size. - Highlights: • I-V characteristics study of NiFe_2O_4 nanoparticles with varying particle sizes. • Experiments evident electrical hysteretic behaviour, i.e., electrical memory effect. • Magnetic field dependent electrical irreversibility is due to magnetostriction. • A phenomenological model has been proposed on the light of induced polarization. • Such electrical irreversibility decreases with increasing particle sizes.

  14. The effect of magnetic stress and stiffness modulus on resonant characteristics of Ni-Mn-Ga ferromagnetic shape memory alloy actuators

    International Nuclear Information System (INIS)

    Techapiesancharoenkij, Ratchatee; Kostamo, Jari; Allen, Samuel M.; O'Handley, Robert C.

    2011-01-01

    The prospect of using ferromagnetic shape memory alloys (FSMAs) is promising for a resonant actuator that requires large strain output and a drive frequency below 1 kHz. In this investigation, three FSMA actuators, equipped with tetragonal off-stoichiometric Ni 2 MnGa single crystals, were developed to study their frequency response and resonant characteristics. The first actuator, labeled as A1, was constructed with low-k bias springs and one Ni-Mn-Ga single crystal. The second actuator, labeled as A2, was constructed with high-k bias springs and one Ni-Mn-Ga crystal. The third actuator, labeled as A3, was constructed with high-k bias springs and two Ni-Mn-Ga crystals connected in parallel. The three actuators were magnetically driven over the frequency range of 10 Hz-1 kHz under 2 and 3.5 kOe magnetic-field amplitudes. The field amplitude of 2 kOe is insufficient to generate significant strain output from all three actuators; the maximum magnetic-field-induced strain (MFIS) at resonance is 2%. The resonant MFIS output improves to 5% under 3.5-kOe amplitude. The frequency responses of all three actuators show a strong effect of the spring k constant and the Ni-Mn-Ga modulus stiffness on the resonant frequencies. The resonant frequency of the Ni-Mn-Ga actuator was raised from 450 to 650 Hz by increasing bias spring k constant and/or the number of Ni-Mn-Ga crystals. The higher number of the Ni-Mn-Ga crystals not only increases the magnetic force output but also raises the total stiffness of the actuator resulting in a higher resonant frequency. The effective modulus of the Ni-Mn-Ga is calculated from the measured resonant frequencies using the mass-spring equation; the calculated modulus values for the three actuators fall in the range of 50-60 MPa. The calculated effective modulus appears to be close to the average modulus value between the low twinning modulus and high elastic modulus of the untwined Ni-Mn-Ga crystal. - Highlights: → Dynamic FSMA actuation shows

  15. Alloying effect on K shell X-ray fluorescence cross-sections and yields in Ti-Ni based shape memory alloys

    Directory of Open Access Journals (Sweden)

    Bünyamin Alım

    2018-04-01

    Full Text Available K shell X-ray fluorescence cross-sections (σKα, σKβ and σK, and K shell fluorescence yields (ωK of Ti, Ni both in pure metals and in different alloy compositions (TixNi1-x; x = 0.3, 0.4, 0.5, 0.6, 0.7 were measured by using energy dispersive X-ray fluorescence (EDXRF technique. The samples were excited by 22.69 keV X-rays from a 10 mCi Cd-109 radioactive point source and K X rays emitted by samples were counted by a high resolution Si(Li solid-state detector coupled to a 4 K multichannel analyzer (MCA. The alloying effects on the X-ray fluorescence (XRF parameters of Ti-Ni shape memory alloys (SMAs were investigated. It is clearly observed that alloying effect causes to change in K shell XRF parameter values in Ti-Ni based SMAs for different compositions of x. Also, the present investigation makes it possible to perform reliable interpretation of experimental σKα, σKβ and ωK values for Ti and Ni in SMAs and can also provide quantitative information about the changes of K shell X-ray fluorescence cross sections and fluorescence yields of these metals with alloy composition. Keywords: Alloying effect, XRF, K X-ray fluorescence cross-section, K shell fluorescence yield, Shape memory alloy

  16. Shape Memory Characteristics of Ti(sub 49.5)Ni(sub 25)Pd(sub 25)Sc(sub 0.5) High-Temperature Shape Memory Alloy After Severe Plastic Deformation

    Science.gov (United States)

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

    2011-01-01

    A Ti(49.5)Ni25Pd25Sc(0.5) high-temperature shape memory alloy is thermomechanically processed to obtain enhanced shape-memory characteristics: in particular, dimensional stability upon repeated thermal cycles under constant loads. This is accomplished using severe plastic deformation via equal channel angular extrusion (ECAE) and post-processing annealing heat treatments. The results of the thermomechanical experiments reveal that the processed materials display enhanced shape memory response, exhibiting higher recoverable transformation and reduced irrecoverable strain levels upon thermal cycling compared with the unprocessed material. This improvement is attributed to the increased strength and resistance of the material against defect generation upon phase transformation as a result of the microstructural refinement due to the ECAE process, as supported by the electron microscopy observations.

  17. Influence of compressive load conditions and thickness on the two-way shape memory behavior in tube-shaped NiTi alloy

    International Nuclear Information System (INIS)

    Yoo, Young Ik; Shin, Dong Kil; Lee, Jung Ju; Lee, Chang Ho

    2012-01-01

    The two-way shape memory behavior of Ni 55 Ti 45 was investigated to develop a tube-shaped NiTi actuator which could generate a large amount of force. The two-way shape memory effect (TWSME) was induced by thermal cycling under various amounts of constant compressive stress. Six specimens with the same outer diameter and different thickness were used to apply the TWSME to an actuator. A fast saturation tendency of the recovery strain was shown through training at each level of constant stress, after which the two-way shape memory strain was quantitatively measured during thermal cycling for each level of applied stress. From the results, the maximum two-way strain value was obtained after training at a constant level of stress and then decreased thereafter. In addition, the two-way strain was found to depend on the thickness of the tube-shaped specimen. All specimens could be divided into two groups depending on the rate of increase in the two-way strain. After two-way strain was obtained, the two-way recovery stress was measured to verify the performance of the sample as an actuator. The results showed that the two-way recovery stress behavior was similar to the two-way strain; if the optimal thickness of the specimen and the stress applied for training are used for the development of the TWSME, tube-shaped NiTi using the TWSME can replace one-way shape memory alloys. (paper)

  18. Influence of grain size on the electrochemical properties of LaNi3.55 AL0.3 Mn0.4 Co0.75 compound use for Ni-MH battery

    International Nuclear Information System (INIS)

    Luu Tuan Tai; Tran Bao Trung; Than Duc Hien; Luu Hoai Nam

    2007-01-01

    In this work, LaNi 3.55 Al 0.3 Mn 0.4 Co 0.75 compounds were prepared by are melting method in the Ar atmosphere. The structure and grain size were tested by X-ray diffraction and TEM measurements. Electrochemical properties and battery parameter were carried out by bipotentiostat and battery tester equipment s. The results show that with the grain size 50 μm, capacity of the negative electrode reduces to 40 nm, the capacity rapidly increase to 170 mAh/g and other battery parameter also improve. (author)

  19. NiTi shape-memory alloy oxidized in low-temperature plasma with carbon coating: Characteristic and a potential for cardiovascular applications

    Science.gov (United States)

    Witkowska, Justyna; Sowińska, Agnieszka; Czarnowska, Elżbieta; Płociński, Tomasz; Borowski, Tomasz; Wierzchoń, Tadeusz

    2017-11-01

    Surface layers currently produced on NiTi alloys do not meet all the requirements for materials intended for use in cardiology. Plasma surface treatments of titanium and its alloys under glow discharge conditions make it possible to produce surface layers, such as TiN or TiO2, which increases corrosion resistance and biocompatibility. The production of layers on NiTi alloys with the same properties, and maintaining their shape memory and superelasticity features, requires the use of low-temperature processes. At the same time, since it is known that the carbon-based layers could prevent excessive adhesion and aggregation of platelets, we examined the composite a-CNH + TiO2 type surface layer produced by means of a hybrid method combining oxidation in low-temperature plasma and Radio Frequency Chemical Vapor Deposition (RFCVD) processes. Investigations have shown that this composite layer increases the corrosion resistance of the material, and both the low degree of roughness and the chemical composition of the surface produced lead to decreased platelet adhesion and aggregation and proper endothelialization, which could extend the range of applications of NiTi shape memory alloys.

  20. Phase volume fractions and strain measurements in an ultrafine-grained NiTi shape-memory alloy during tensile loading

    International Nuclear Information System (INIS)

    Young, M.L.; Wagner, M.F.-X.; Frenzel, J.; Schmahl, W.W.; Eggeler, G.

    2010-01-01

    An ultrafine-grained pseudoelastic NiTi shape-memory alloy wire with 50.9 at.% Ni was examined using synchrotron X-ray diffraction during in situ uniaxial tensile loading (up to 1 GPa) and unloading. Both macroscopic stress-strain measurements and volume-averaged lattice strains are reported and discussed. The loading behavior is described in terms of elasto-plastic deformation of austenite, emergence of R phase, stress-induced martensitic transformation, and elasto-plastic deformation, grain reorientation and detwinning of martensite. The unloading behavior is described in terms of stress relaxation and reverse plasticity of martensite, reverse transformation of martensite to austenite due to stress relaxation, and stress relaxation of austenite. Microscopically, lattice strains in various crystallographic directions in the austenitic B2, martensitic R, and martensitic B19' phases are examined during loading and unloading. It is shown that the phase transformation occurs in a localized manner along the gage length at the plateau stress. Phase volume fractions and lattice strains in various crystallographic reflections in the austenite and martensite phases are examined over two transition regions between austenite and martensite, which have a width on the order of the wire diameter. Anisotropic effects observed in various crystallographic reflections of the austenitic phase are also discussed. The results contribute to a better understanding of the tensile loading behavior, both macroscopically and microscopically, of NiTi shape-memory alloys.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-12-15

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

  2. Multiscale Modeling of Polycrystalline NiTi Shape Memory Alloy under Various Plastic Deformation Conditions by Coupling Microstructure Evolution and Macroscopic Mechanical Response.

    Science.gov (United States)

    Hu, Li; Jiang, Shuyong; Zhou, Tao; Tu, Jian; Shi, Laixin; Chen, Qiang; Yang, Mingbo

    2017-10-13

    Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA) are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM). Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD) density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.

  3. Multiscale Modeling of Polycrystalline NiTi Shape Memory Alloy under Various Plastic Deformation Conditions by Coupling Microstructure Evolution and Macroscopic Mechanical Response

    Directory of Open Access Journals (Sweden)

    Li Hu

    2017-10-01

    Full Text Available Numerical modeling of microstructure evolution in various regions during uniaxial compression and canning compression of NiTi shape memory alloy (SMA are studied through combined macroscopic and microscopic finite element simulation in order to investigate plastic deformation of NiTi SMA at 400 °C. In this approach, the macroscale material behavior is modeled with a relatively coarse finite element mesh, and then the corresponding deformation history in some selected regions in this mesh is extracted by the sub-model technique of finite element code ABAQUS and subsequently used as boundary conditions for the microscale simulation by means of crystal plasticity finite element method (CPFEM. Simulation results show that NiTi SMA exhibits an inhomogeneous plastic deformation at the microscale. Moreover, regions that suffered canning compression sustain more homogeneous plastic deformation by comparison with the corresponding regions subjected to uniaxial compression. The mitigation of inhomogeneous plastic deformation contributes to reducing the statistically stored dislocation (SSD density in polycrystalline aggregation and also to reducing the difference of stress level in various regions of deformed NiTi SMA sample, and therefore sustaining large plastic deformation in the canning compression process.

  4. In Situ Neutron Diffraction Analyzing Stress-Induced Phase Transformation and Martensite Elasticity in [001]-Oriented Co49Ni21Ga30 Shape Memory Alloy Single Crystals

    Science.gov (United States)

    Reul, A.; Lauhoff, C.; Krooß, P.; Gutmann, M. J.; Kadletz, P. M.; Chumlyakov, Y. I.; Niendorf, T.; Schmahl, W. W.

    2018-02-01

    Recent studies demonstrated excellent pseudoelastic behavior and cyclic stability under compressive loads in [001]-oriented Co-Ni-Ga high-temperature shape memory alloys (HT-SMAs). A narrow stress hysteresis was related to suppression of detwinning at RT and low defect formation during phase transformation due to the absence of a favorable slip system. Eventually, this behavior makes Co-Ni-Ga HT-SMAs promising candidates for several industrial applications. However, deformation behavior of Co-Ni-Ga has only been studied in the range of theoretical transformation strain in depth so far. Thus, the current study focuses not only on the activity of elementary deformation mechanisms in the pseudoelastic regime up to maximum theoretical transformation strains but far beyond. It is shown that the martensite phase is able to withstand about 5% elastic strain, which significantly increases the overall deformation capability of this alloy system. In situ neutron diffraction experiments were carried out using a newly installed testing setup on Co-Ni-Ga single crystals in order to reveal the nature of the stress-strain response seen in the deformation curves up to 10% macroscopic strain.

  5. Martensitic transformation and phase stability of In-doped Ni-Mn-Sn shape memory alloys from first-principles calculations

    International Nuclear Information System (INIS)

    Xiao, H. B.; Yang, C. P.; Wang, R. L.; Luo, X.; Marchenkov, V. V.

    2014-01-01

    The effect of the alloying element Indium (In) on the martensitic transition, magnetic properties, and phase stabilities of Ni 8 Mn 6 Sn 2−x In x shape memory alloys has been investigated using the first-principles pseudopotential plane-wave method based on density functional theory. The energy difference between the austenitic and martensitic phases was found to increase with increasing In content, which implies an enhancement of the martensitic phase transition temperature (T M ). Moreover, the formation energy results indicate that In-doping increases the relative stability of Ni 8 Mn 6 Sn 2−x In x both in austenite and martensite. This results from a reduction in density of states near the Fermi level regions caused by Ni-3d–In-5p hybridization when Sn is replaced by In. The equilibrium equation of state results show that the alloys Ni 8 Mn 6 Sn 2−x In x exhibit an energetically degenerated effect for an In content of x = ∼1.5. This implies the coexistence of antiparallel and parallel configurations in the austenite.

  6. Synthesis, characterization and performance of CoxNi1−xS compounds for application in lithium batteries

    Directory of Open Access Journals (Sweden)

    Atef Y. Shenouda

    2017-06-01

    Full Text Available This study reports a process to prepare CoxNi1−xS (x = 0, 0.25, 0.5, 0.75 and 1 samples by hydrothermal process at 250 °C using stoichiometric weight ratios of raw materials. The prepared powder samples were annealed in Ar atmosphere at 450 °C for 3 h. The crystal structure of prepared annealed CoxNi1−xS samples was characterized by XRD. SEM investigations were carried out explaining the morphology of these samples. Electrochemical impedance spectra (EIS measurements, Cyclic voltammetric (CV and galvanostatic measurements were carried out. The life cycle performance was carried out for the cells and Li/Co0.25Ni0.75S cell gave specific discharge capacities of about 330 mA h g−1.

  7. Segregation and microstructure evolution in chill cast and directionally solidified Ni-Mn-Sn metamagnetic shape memory alloys

    Science.gov (United States)

    Czaja, P.; Wierzbicka-Miernik, A.; Rogal, Ł.

    2018-06-01

    A multiphase solidification behaviour is confirmed for a range of Ni-rich and Ni-deficient Ni-Mn-Sn induction cast and directionally solidified (Bridgman) alloys. The composition variation is primarily linked to the changing Mn/Sn ratio, whereas the content of Ni remains largely stable. The partitioning coefficients for the Ni50Mn37Sn13 and Ni46Mn41.5Sn12.5 Bridgman alloys were obtained according to the Scheil equation based on the composition distribution along the longitudinal cross section of the ingots. Homogenization heat treatment performed for 72 h at 1220 K turned out sufficient for ensuring chemical uniformity on the macro- and microscale. It is owed to a limited segregation length scale due to slow cooling rates adopted for the directional solidification process.

  8. Rapid thermal annealing of Ti-rich TiNi thin films: A new approach to fabricate patterned shape memory thin films

    International Nuclear Information System (INIS)

    Motemani, Y.; Tan, M.J.; White, T.J.; Huang, W.M.

    2011-01-01

    This paper reports the rapid thermal annealing (RTA) of Ti-rich TiNi thin films, synthesized by the co-sputtering of TiNi and Ti targets. Long-range order of aperiodic alloy could be achieved in a few seconds with the optimum temperature of 773 K. Longer annealing (773 K/240 s), transformed the film to a poorly ordered vitreous phase, suggesting a novel method for solid state amorphization. Reitveld refinement analyses showed significant differences in structural parameters of the films crystallized by rapid and conventional thermal annealing. Dependence of the elastic modulus on the valence electron density (VED) of the crystallized films was studied. It is suggested that RTA provides a new approach to fabricate patterned shape memory thin films.

  9. The effects of vacuum induction melting and electron beam melting techniques on the purity of NiTi shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Otubo, J. [Instituto Tecnologico de Aeronautica (ITA), 12228-900 S.J. Campos, SP (Brazil) and DEMA-FEM-UNICAMP, 13083-000 Campinas, SP (Brazil)]. E-mail: jotubo@ita.br; Rigo, O.D. [DEMA-FEM-UNICAMP, 13083-000 Campinas, SP (Brazil); Neto, C. Moura [Instituto Tecnologico de Aeronautica (ITA), 12228-900 S.J. Campos, SP (Brazil); Mei, P.R. [DEMA-FEM-UNICAMP, 13083-000 Campinas, SP (Brazil)

    2006-11-25

    The usual process to produce NiTi shape memory alloys is by vacuum induction melting (VIM) using graphite crucible that contaminates the bath with carbon. The contamination by oxygen comes from residual oxygen inside the melting chamber. A new alternative process to produce NiTi alloys is by electron beam melting (EBM) using water-cooled copper crucible that eliminates the carbon contamination and the oxygen contamination would be minimized due to operation in high vacuum. This work compares the two processes and shows that the carbon contamination is four to ten times lower for EBM compared to VIM products and that the final oxygen content is much more dependent on the starting raw materials. The purity of the final product should be very important mainly in terms of biomedical applications and the contaminations by carbon and oxygen affect the direct and reverse martensitic transformation temperatures.

  10. Experimental observations on uniaxial whole-life transformation ratchetting and low-cycle stress fatigue of super-elastic NiTi shape memory alloy micro-tubes

    Science.gov (United States)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-07-01

    In this work, the low-cycle fatigue failure of super-elastic NiTi shape memory alloy micro-tubes with a wall thickness of 150 μm is investigated by uniaxial stress-controlled cyclic tests at human body temperature 310 K. The effects of mean stress, peak stress, and stress amplitude on the uniaxial whole-life transformation ratchetting and fatigue failure of the NiTi alloy are observed. It is concluded that the fatigue life depends significantly on the stress levels, and the extent of martensite transformation and its reverse play an important role in determining the fatigue life. High peak stress or complete martensite transformation shortens the fatigue life.

  11. Experimental observations on uniaxial whole-life transformation ratchetting and low-cycle stress fatigue of super-elastic NiTi shape memory alloy micro-tubes

    International Nuclear Information System (INIS)

    Song, Di; Kang, Guozheng; Kan, Qianhua; Yu, Chao; Zhang, Chuanzeng

    2015-01-01

    In this work, the low-cycle fatigue failure of super-elastic NiTi shape memory alloy micro-tubes with a wall thickness of 150 μm is investigated by uniaxial stress-controlled cyclic tests at human body temperature 310 K. The effects of mean stress, peak stress, and stress amplitude on the uniaxial whole-life transformation ratchetting and fatigue failure of the NiTi alloy are observed. It is concluded that the fatigue life depends significantly on the stress levels, and the extent of martensite transformation and its reverse play an important role in determining the fatigue life. High peak stress or complete martensite transformation shortens the fatigue life. (paper)

  12. Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni{sub 50.3}Ti{sub 34.7}Zr{sub 15} shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Evirgen, A. [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States); Karaman, I., E-mail: ikaraman@tamu.edu [Department of Materials Science and Engineering, Texas A& M University, College Station, TX 77843 (United States); Pons, J.; Santamarta, R. [Departament de Fisica, Universitat de les Illes Balears, E07122 Palma de Mallorca (Spain); Noebe, R.D. [Materials and Structures Division, NASA Glenn Research Center, Cleveland, OH 44135 (United States)

    2016-02-08

    The microstructure and shape memory characteristics of the Ni{sub 50.3}Ti{sub 34.7}Zr{sub 15} shape memory alloy were investigated as a function of aging heat treatments that result in nanometer to submicron size precipitates. Microstructure–property relationships were developed by characterizing samples using transmission electron microscopy, differential scanning calorimetry, and load-biased thermal cycling experiments. The precipitate size was found to strongly influence the martensitic transformation–precipitate interactions and ultimately the shape memory characteristics of the alloy. Aging treatments resulting in relatively fine precipitates, which are not an obstacle to twin boundaries and easily bypassed by martensite variants, exhibited higher transformation strain, lower transformation thermal hysteresis, and better thermal and dimensional stability compared to samples with relatively large precipitates. When precipitate dimensions approached several hundred nanometers in size they acted as obstacles to martensite growth, limiting martensite variant and twin size resulting in reduced functional and structural properties. Aging heat treatments were also shown to result in a wide range of transformation temperatures, increasing them above 100 °C in some cases, and affected the stress dependence of the transformation hysteresis and the stress versus transformation temperature relationships for the Ni{sub 50.3}Ti{sub 34.7}Zr{sub 15} alloy.

  13. Role of nano-precipitation on the microstructure and shape memory characteristics of a new Ni_5_0_._3Ti_3_4_._7Zr_1_5 shape memory alloy

    International Nuclear Information System (INIS)

    Evirgen, A.; Karaman, I.; Pons, J.; Santamarta, R.; Noebe, R.D.

    2016-01-01

    The microstructure and shape memory characteristics of the Ni_5_0_._3Ti_3_4_._7Zr_1_5 shape memory alloy were investigated as a function of aging heat treatments that result in nanometer to submicron size precipitates. Microstructure–property relationships were developed by characterizing samples using transmission electron microscopy, differential scanning calorimetry, and load-biased thermal cycling experiments. The precipitate size was found to strongly influence the martensitic transformation–precipitate interactions and ultimately the shape memory characteristics of the alloy. Aging treatments resulting in relatively fine precipitates, which are not an obstacle to twin boundaries and easily bypassed by martensite variants, exhibited higher transformation strain, lower transformation thermal hysteresis, and better thermal and dimensional stability compared to samples with relatively large precipitates. When precipitate dimensions approached several hundred nanometers in size they acted as obstacles to martensite growth, limiting martensite variant and twin size resulting in reduced functional and structural properties. Aging heat treatments were also shown to result in a wide range of transformation temperatures, increasing them above 100 °C in some cases, and affected the stress dependence of the transformation hysteresis and the stress versus transformation temperature relationships for the Ni_5_0_._3Ti_3_4_._7Zr_1_5 alloy.

  14. The effect of compositional changes on the structural and hydrogen storage properties of (La–Ce)Ni5 type intermetallics towards compounds suitable for metal hydride hydrogen compression

    International Nuclear Information System (INIS)

    Odysseos, M.; De Rango, P.; Christodoulou, C.N.; Hlil, E.K.; Steriotis, T.; Karagiorgis, G.; Charalambopoulou, G.; Papapanagiotou, T.; Ampoumogli, A.; Psycharis, V.; Koultoukis, E.; Fruchart, D.; Stubos, A.

    2013-01-01

    Graphical abstract: The effect of the partial substitution of La with Ce on the crystal structure and the final hydrogen storage properties of the alloys. Highlights: ► Absorption-based systems exploit the properties of reversible metal hydrides. ► AB5 intermetallics are mostly popular for thermal desorption compressors. ► Investigation of H2 absorption/desorption properties of LaNi5 and its derivatives. ► LaNi5 thermodynamic properties adjustment by partially replacing La with rare earths. -- Abstract: The present work has been aiming at the synthesis and study of a series of La 1−x Ce x Ni 5 (x = 0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8) alloys in an attempt to investigate possible alterations of the hydrogen absorption/desorption properties The alloys were prepared by induction melting of the constituent elements. The systematic characterization of all new compounds by means of XRD and hydrogen sorption measurements revealed the effect of the partial substitution of La with Ce on the crystal structure and the final hydrogen storage properties of the alloys. Extensive absorption/desorption experiments (Van’t Hoff diagrams) have shown that such alloys can be used to build a metal hydride compressor (MHC), compressing H 2 gas from 0.2 MPa to 4.2 MPa using cold (20 °C) and hot (80 °C) water

  15. Development of Ni-Based Catalysts Derived from Hydrotalcite-Like Compounds Precursors for Synthesis Gas Production via Methane or Ethanol Reforming

    Directory of Open Access Journals (Sweden)

    Ya-Li Du

    2017-02-01

    Full Text Available As a favorably clean fuel, syngas (synthesis gas production has been the focus of concern in past decades. Substantial literatures reported the syngas production by various catalytic reforming reactions particularly in methane or ethanol reforming. Among the developed catalysts in these reforming processes, Ni-based catalysts from hydrotalcite-like compounds (HTLcs precursors have drawn considerable attention for their preferable structural traits. This review covers the recent literature reporting syngas production with Ni-based catalysts from HTLc precursors via methane or ethanol reforming. The discussion was initiated with catalyst preparation (including conventional and novel means, followed by subsequent thermal treatment processes, then composition design and the addition of promoters in these catalysts. As Ni-based catalysts have thermodynamic potential to deactivate because of carbon deposition or metal sintering, measures for dealing with these problems were finally summarized. To obtain optimal catalytic performances and resultantly better syngas production, based on analyzing the achievements of the references, some perspectives were finally proposed.

  16. Study of the behavior of the compound Mg2Ni0.5Co0.5 front to hydriding process

    International Nuclear Information System (INIS)

    Martinez, C; Ordonez, S; Serafini, D; Guzman, D; Bustos, O

    2012-01-01

    This paper study the behavior of the compound Mg 2 Ni 0,5 Co 0,5 during the hydriding process. Elemental powders of Mg, Ni and Co, with an atomic ratio of 2:0,5:0,5 were mechanically alloyed using a high energy mill SPEX 8000D for 36h. The amorphous and crystalline structure of the samples was characterized through X-ray diffraction The hydriding process was performed by the volumetric technique Sievert at 90 o C and a pressure of 20 bar H 2 . The desorption process was evaluated by differential scanning calorimetry. Based on the results we can conclude that the amorphous structure absorbs more hydrogen, reaching a maximum of 3.6 wt% H2, besides the incorporation of cobalt act as catalyst for the absorption of H2 obtaining values higher than those reported in the Mg-Ni system amorphous state. The desorption process is influenced by the type of structure that presents the alloy

  17. The effect of the melt spinning processing parameters on the solidification structures in Ti-30 at.% Ni-20 at.% Cu shape memory alloys

    International Nuclear Information System (INIS)

    Kim, Yeon-wook; Yun, Young-mok; Nam, Tae-hyun

    2006-01-01

    Solidification structures and shape memory characteristics of Ti-30 at.% Ni-20 at.% Cu alloy ribbons prepared by melt spinning were investigated by means of differential scanning calorimetry and X-ray diffraction. In these experiments particular attention has been paid to change the ejection temperature of the melt from 1350 to 1500 deg. C and the velocity of cooling wheel from 33 to 55 m/s. Then the cooling rates of ribbons were controlled. The effect of this cooling rate on solidification structures and martensitic transformation behaviors is discussed

  18. Optical microscope study of the γ(FCC)ε(HC) martensitic transformation of a Fe-16%Mn-9%Cr-5%Si-4%Ni shape memory alloy

    International Nuclear Information System (INIS)

    Bergeon, N.; Guenin, G.

    1995-01-01

    The γ(FCC) ε(HC) transformation is studied by light optical microscopy and scanning electron microscopy in a polycrystalline Fe-Mn-Si-Cr-Ni shape memory alloy. Thermal and stress-induced martensites are both studied to point out differences. A color etching method permitted to clearly observe morphological evolutions during the transformation and its reversion. Deformations of a golden microgrid deposed on austenitic samples are observed by SEM during the transformation. This technic has led to point out microscopic differences concerning the two kinds of martensite. SEM results are used to explain light optical microscopy observations. (orig.)

  19. 'In situ' and 'Post-mortem' TEM study of the super-elastic effect in Cu-Al-Ni shape memory alloys

    International Nuclear Information System (INIS)

    Ibarra, A.; San Juan, J.; Bocanegra, E.H.; Caillard, D.; No, M.L.

    2006-01-01

    An analysis of the microstructure evolution during super-elastic cycling has been performed by transmission electron microscopy (TEM) in order to understand the physical mechanism responsible for the thermo-mechanical properties evolution, as well as the martensitic transformation ageing. Particularly, in this work we have studied the super-elastic effect in Cu-Al-Ni shape memory alloys by 'in situ' TEM experiments. The bright field images and diffraction patterns have allowed us to determine, during the transformation, the kind of nucleated martensite variants and their relative orientations. Finally, we have analysed the super-elastic effect on the dislocation microstructure and on the transformation temperatures

  20. Determining Recoverable and Irrecoverable Contributions to Accumulated Strain in a NiTiPd High-Temperature Shape Memory Alloy During Thermomechanical Cycling

    Science.gov (United States)

    Monroe, J. A.; Karaman, I.; Lagoudas, D. C.; Bigelow, G.; Noebe, R. D.; Padula, S., II

    2011-01-01

    When Ni(29.5)Ti(50.5)Pd30 shape memory alloy is thermally cycled under stress, significant strain can accumulate due to elasticity, remnant oriented martensite and plasticity. The strain due to remnant martensite can be recovered by further thermal cycling under 0 MPa until the original transformation-induced volume change and martensite coefficient of thermal expansion are obtained. Using this technique, it was determined that the 8.15% total accumulated strain after cycling under 200 MPa consisted of 0.38%, 3.97% and 3.87% for elasticity, remnant oriented martensite and creep/plasticity, respectively.

  1. Phase transformations in Zr-29.56 at.% Cu-19.85 at.% Ni melt-spun high-temperature shape memory alloy

    International Nuclear Information System (INIS)

    Firstov, G.S.; Koval, Yu.N.; Van Humbeeck, J.; Portier, R.; Vermaut, P.; Ochin, P.

    2006-01-01

    The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed

  2. Phase transformations in Zr-29.56 at.% Cu-19.85 at.% Ni melt-spun high-temperature shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Firstov, G.S. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine)]. E-mail: gfirst@imp.kiev.ua; Koval, Yu.N. [Institute for Metal Physics, National Academy of Sciences, 36 Vernadsky blvd., UA-03680, Kiev-142 (Ukraine); Van Humbeeck, J. [Department MTM, Catholic University of Leuven, Kasteelpark Arenberg 44, B-3001 Heverlee (Leuven) (Belgium); Portier, R. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Vermaut, P. [Laboratoire de Metallurgie Structurale ENSCP, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Ochin, P. [Centre d' Etudes de Chimie Metallurgique-CNRS UPR2801, 15 rue Georges Urbain, 94407 Vitry-sur-Seine (France)

    2006-11-25

    The present paper focuses on the phase transformations during crystallization of the melt-spun Zr-29.56 at.% Cu-19.85 at.% Ni high-temperature shape memory alloy (HTSMA). This alloy exhibits a martensitic transformation in the bulk polycrystalline state at temperatures above crystallization of the metallic glass with the same composition. The crystallization kinetics were investigated by differential scanning calorimetry. The intermediate and final products of crystallization for this HTSMA were studied by means of transmission electron microscopy. The chain of the transformations starting from crystallization and ending at martensitic transformation will be described. Perspectives of the thin film production of Zr-based HTSMA will be discussed.

  3. The crystal structure and electronic properties of a new metastable non-stoichiometric BaAl{sub 4}-type compound crystallized from amorphous La{sub 6}Ni{sub 34}Ge{sub 60} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Hasegawa, Masashi [Institute for Materials Research, Tohoku University, Sendai, Katahira 980-8577 (Japan); Suzuki, Shoichiro [Institute for Materials Research, Tohoku University, Sendai, Katahira 980-8577 (Japan); Ohsuna, Tetsu [Institute for Materials Research, Tohoku University, Sendai, Katahira 980-8577 (Japan); Matsubara, Eiichiro [Institute for Materials Research, Tohoku University, Sendai, Katahira 980-8577 (Japan); Endo, Satoshi [Center for Low Temperature Science, Tohoku University, Sendai, Katahira 980-8577 (Japan); Inoue, Akihisa [Institute for Materials Research, Tohoku University, Sendai, Katahira 980-8577 (Japan)

    2004-11-17

    A new metastable La-Ge-Ni ternary BaAl{sub 4}-type (ThCr{sub 2}Si{sub 2}-type) compound, of which the space group is I4/mmm is synthesized. It is obtained by a polymorphic transformation from an La{sub 6}Ni{sub 34}Ge{sub 60} amorphous alloy on crystallizing. The formula of the compound is (La{sub 0.3}Ge{sub 0.7})(Ni{sub 0.85}Ge{sub 0.15}){sub 2}Ge{sub 2}. This indicates that it is highly non-stoichiometric compared to the stoichiometric LaNi{sub 2}Ge{sub 2}. It is found that the c-axis lattice parameter of this compound is much longer than that of LaNi{sub 2}Ge{sub 2}. It should be noted that the longer c-axis unit cell parameter is attributable only to the longer interlayer distance between Ge site and Ni site layers. The temperature dependences of electrical resistivity and thermoelectric power of the (La{sub 0.3}Ge{sub 0.7})(Ni{sub 0.85}Ge{sub 0.15}){sub 2}Ge{sub 2} compound and La{sub 6}Ni{sub 34}Ge{sub 60} amorphous alloy are also clarified. The comparison of these electronic properties between the two materials indicates that sp-electrons mainly contribute to the density of states around the Fermi level of this compound.

  4. Crystal structure of R.E. NiSn and R.E. PdSn equiatomic compounds

    International Nuclear Information System (INIS)

    Dwight, A.E.

    1983-03-01

    Call constants and volume per formula weight are tabulated for RE NiSn (RE = La to Lu, Y) and RE PdSn (RE = Nd to Ho). The unit cell constants are also plotted versus ionic radius of the RE; trends are noted

  5. Synthesis and chemical recycling of high polymers using C1 compounds; C1 kagobutsu ni yoru kobunshi no chemical recycle

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, T. [National Institute of Materials and Chemical Research, Tsukuba (Japan)

    1997-09-01

    The paper outlined a study of the synthesis of high polymers using C1 compounds which are continuously usable chemical materials and the related compounds such as the derivatives, and also the chemical recycle. In the case of waste plastics mixed in urban refuse, effective is the chemical recycle where C1 compounds obtained by gasifying the mixed waste are used as high polymer material. For the synthesis and recycle of high polymers using C1 compounds, there are three routes: Route A (recycle via high polymer materials), Route B (recycle via C1 compounds and high polymer materials), and Route C including global-scale carbon recycle (recycle via carbon dioxide from biodegradable plastics using microorganism). Among high polymers, those that can be synthesized from C1 compounds, for example, polymethylene, polyacetal and polyketone can be chemically recycled by Route B. 30 refs., 2 figs., 1 tab.

  6. Resonance spin memory in low-energy gamma-ray spectra from Sb, Tb, Ho and Ta odd-odd compound nuclei

    International Nuclear Information System (INIS)

    Olejniczak, U.; Gundorin, N.A.; Pikelner, L.B.; Serov, D.G.; Przytula, M.

    2002-01-01

    The low-energy gamma-ray spectra from neutron resonance capture with natural samples of Sb, Tb, Ho and Ta were measured using a HPGe detector at the IBR-30 pulsed reactor (JINR, Dubna). The resonance spin memory effect in the spectra from the odd-odd compound nuclei of 122 Sb, 160 Tb and 166 Ho was found to be quite distinct. For the 182 Ta compound nucleus it proved to be rather weak

  7. An overview of NiTi shape memory alloy: Corrosion resistance and antibacterial inhibition for dental application

    Energy Technology Data Exchange (ETDEWEB)

    Fadlallah, Sahar A., E-mail: sahar.fadlallah@yahoo.com [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Chemistry Department, Faculty of Science, Cairo University, Cairo (Egypt); El-Bagoury, Nader [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Casting Technology Lab., Manufacturing Technology Dept., CMRDI, P.O. Box 87, Helwan, Cairo (Egypt); Gad El-Rab, Sanaa M.F. [Biotechnology Department, Faculty of Science, Taif University, Taif (Saudi Arabia); Botany Department, Faculty of Science, Asuit University, Asuit (Egypt); Ahmed, Rasha A. [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia); Forensic Chemistry Laboratories, Medico Legal Department, Ministry of Justice, Cairo (Egypt); El-Ousamii, Ghaida [Materials and Corrosion Lab. (MCL), Faculty of Science, Taif University, Taif (Saudi Arabia)

    2014-01-15

    Highlights: • Evaluate the corrosion resistance of NiTi alloy by using electrochemical techniques. • Estimate the Antibacterial inhibition rate of NiTi alloy. • Assessment the mechanical properties of NiTi from the hardness measurements. • Comparsion the microstructures of cast NiTi with Ti, this indicate the role of Ni to change the behavior of alloy in oral environment. • Advise drinking green tea in small quantities in small quantities in the event of present NiTi alloy in the oral cavity. • Recommendation to use NiTi for dental application. -- Abstract: Nowadays, Nickel–titanium nearly equiatomic is considered as one of the best biomaterials. The aim of the present work deals with the evolution of the electrochemical behavior of NiTi in simulated oral environment. The hardness, microstructures corrosion resistance and antibacterial performance of NiTi alloy were compared with pure titanium. The hardness of NiTi is twice the hardness of pure titanium. Electrochemical techniques were used to detect the corrosion resistance of both biomaterials in Hank’s solution containing (−)-epigallocatechin gallate (EGCG) which used to simulate the oral environment. In the physiological solution selected for the present study, the impedance spectroscopy (EIS) results showed that EGCG sharply increase the corrosion resistance of NiTi from 129 kΩ cm{sup 2} to 1.10 T Ω cm{sup 2} while slowly increase the corrosion resistance of pure titanium from 9.4 kΩ cm{sup 2} to 11.3 kΩ cm{sup 2} during the duration time of immersion at 37 °C. The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC 6538). Among the two specimens of biomaterials studied, the antibacterial performance results revealed that the NiTi alloy is better than the pure titanium. The morphology and chemical structure of NiTi and Ti samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X

  8. An overview of NiTi shape memory alloy: Corrosion resistance and antibacterial inhibition for dental application

    International Nuclear Information System (INIS)

    Fadlallah, Sahar A.; El-Bagoury, Nader; Gad El-Rab, Sanaa M.F.; Ahmed, Rasha A.; El-Ousamii, Ghaida

    2014-01-01

    Highlights: • Evaluate the corrosion resistance of NiTi alloy by using electrochemical techniques. • Estimate the Antibacterial inhibition rate of NiTi alloy. • Assessment the mechanical properties of NiTi from the hardness measurements. • Comparsion the microstructures of cast NiTi with Ti, this indicate the role of Ni to change the behavior of alloy in oral environment. • Advise drinking green tea in small quantities in small quantities in the event of present NiTi alloy in the oral cavity. • Recommendation to use NiTi for dental application. -- Abstract: Nowadays, Nickel–titanium nearly equiatomic is considered as one of the best biomaterials. The aim of the present work deals with the evolution of the electrochemical behavior of NiTi in simulated oral environment. The hardness, microstructures corrosion resistance and antibacterial performance of NiTi alloy were compared with pure titanium. The hardness of NiTi is twice the hardness of pure titanium. Electrochemical techniques were used to detect the corrosion resistance of both biomaterials in Hank’s solution containing (−)-epigallocatechin gallate (EGCG) which used to simulate the oral environment. In the physiological solution selected for the present study, the impedance spectroscopy (EIS) results showed that EGCG sharply increase the corrosion resistance of NiTi from 129 kΩ cm 2 to 1.10 T Ω cm 2 while slowly increase the corrosion resistance of pure titanium from 9.4 kΩ cm 2 to 11.3 kΩ cm 2 during the duration time of immersion at 37 °C. The plate-counting method was used to evaluate the antibacterial performance against Staphylococcus aureus (ATCC 6538). Among the two specimens of biomaterials studied, the antibacterial performance results revealed that the NiTi alloy is better than the pure titanium. The morphology and chemical structure of NiTi and Ti samples were systematically investigated by scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDX). The

  9. Memory

    OpenAIRE

    Wager, Nadia

    2017-01-01

    This chapter will explore a response to traumatic victimisation which has divided the opinions of psychologists at an exponential rate. We will be examining amnesia for memories of childhood sexual abuse and the potential to recover these memories in adulthood. Whilst this phenomenon is generally accepted in clinical circles, it is seen as highly contentious amongst research psychologists, particularly experimental cognitive psychologists. The chapter will begin with a real case study of a wo...

  10. Properties of Haldane Excitations and Multiparticle States in the Antiferromagnetic Spin-1 Chain Compound CsNiCl3

    International Nuclear Information System (INIS)

    Kenzelmann, M.; Cowley, R.A.; Buyers, W.J.L.; Tun, Z.; Coldea, Radu; Enderle, M.

    2002-01-01

    We report inelastic time-of-flight and triple-axis neutron scattering measurements of the excitation spectrum of the coupled antiferromagnetic spin-1 Heisenberg chain system CsNiCl 3 . Measurements over a wide range of wave-vector transfers along the chain confirm that above T N CsNiCl 3 is in a quantum-disordered phase with an energy gap in the excitation spectrum. The spin correlations fall off exponentially with increasing distance with a correlation length ζ = 4.0(2) sites at T = 6.2K. This is shorter than the correlation length for an antiferromagnetic spin-1 Heisenberg chain at this temperature, suggesting that the correlations perpendicular to the chain direction and associated with the interchain coupling lower the single-chain correlation length. A multiparticle continuum is observed in the quantum-disordered phase in the region in reciprocal space where antiferromagnetic fluctuations are strongest, extending in energy up to twice the maximum of the dispersion of the well-defined triplet excitations. We show that the continuum satisfies the Hohenberg-Brinkman sum rule. The dependence of the multiparticle continuum on the chain wave vector resembles that of the two-spinon continuum in antiferromagnetic spin-1/2 Heisenberg chains. This suggests the presence of spin-1/2 degrees of freedom in CsNiCl 3 for T ∼< 12 K, possibly caused by multiply frustrated interchain interactions.

  11. Effects of aging on the shape memory and superelasticity behavior of ultra-high strength Ni54Ti46 alloys under compression

    International Nuclear Information System (INIS)

    Kaya, I.; Tobe, H.; Karaca, H.E.; Basaran, B.; Nagasako, M.; Kainuma, R.; Chumlyakov, Y.

    2016-01-01

    This study investigates the effects of aging on the shape memory and superelasticity behavior of a Ni-rich Ni 54 Ti 46 (at%) alloy. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM) and compression test (thermal cycling under stress and superelasticity) were carried out after 3 h agin;g from 450 °C to 600 °C. The alloys show recoverable shape memory effect with transformation strains of about 1% and narrow hysteresis under high stress levels. The work output of 14.1 Jg −1 was observed at an ultra-high stress level of 1500 MPa after 600 °C 3 h aging. 450 °C 3 h aging resulted in a very narrow temperature hysteresis of 8°C under an ultra-high stress level of 1500 MPa. At room temperature, the superelastic response with 4% total strain was obtained even when high stress level of 2000 MPa is applied after 550 °C 3 h aging.

  12. Effects of aging on the shape memory and superelasticity behavior of ultra-high strength Ni{sub 54}Ti{sub 46} alloys under compression

    Energy Technology Data Exchange (ETDEWEB)

    Kaya, I., E-mail: irfan_kaya@anadolu.edu.tr [Department of Mechanical Engineering, Faculty of Engineering, Anadolu University, Eskisehir TR 26555 (Turkey); Tobe, H.; Karaca, H.E. [Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506 (United States); Basaran, B. [Department of Engineering Technology, College of Technology, University of Houston, Houston, TX 77204 (United States); Nagasako, M. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Kainuma, R. [Department of Material Science, Tohoku University, Sendai 980-8579 (Japan); Chumlyakov, Y. [Siberian Physical-Technical Institute at Tomsk State University, Tomsk 634050 (Russian Federation)

    2016-12-15

    This study investigates the effects of aging on the shape memory and superelasticity behavior of a Ni-rich Ni{sub 54}Ti{sub 46} (at%) alloy. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM) and compression test (thermal cycling under stress and superelasticity) were carried out after 3 h agin;g from 450 °C to 600 °C. The alloys show recoverable shape memory effect with transformation strains of about 1% and narrow hysteresis under high stress levels. The work output of 14.1 Jg{sup −1} was observed at an ultra-high stress level of 1500 MPa after 600 °C 3 h aging. 450 °C 3 h aging resulted in a very narrow temperature hysteresis of 8°C under an ultra-high stress level of 1500 MPa. At room temperature, the superelastic response with 4% total strain was obtained even when high stress level of 2000 MPa is applied after 550 °C 3 h aging.

  13. Assessing the morphology of selective laser melted NiTi-scaffolds for a three-dimensional quantification of the one-way shape memory effect

    Science.gov (United States)

    Bormann, Therese; de Wild, Michael; Beckmann, Felix; Müller, Bert

    2013-04-01

    NiTi is promising for the use as bone scaffold, because the pseudoelasticity or the one- and two-way shape memory effect in the physiological window can mechanically stimulate the adherent cells. Such stimuli can enhance osseointegration and might reduce stress shielding associated with load bearing implants. The present study is based on the additive manufacturing technique of selective laser melting (SLM) to fabricate three-dimensional NiTi scaffolds. We demonstrate that the morphology of the scaffolds can be quantified using synchrotron radiation-based micro computed tomography (SRμCT) and sophisticated registration software. Comparing the CAD file with the SLM scaffolds, quality factors are derived. With respect to the CAD file, the overlap corresponds to (92.5 +/- 0.6) %. (7.4 +/- 0.42) % of material was missing and (48.9 +/- 2.3) % of excess material found. This means that the actual scaffold is less porous than expected, a fact that has to be considered for the scaffold design. In order to quantify the shape memory effect during the shape recovery process, we acquired radiographs rotating an initially deformed scaffold in angular steps of 0.2 degree during controlled heating. The continuously acquired radiographs were combined to tomography data, showing that the quality factors evolved with temperature as the scaffold height, measured by conventional thermo-mechanical analysis. Furthermore, the data comprise the presence of compressive and tensile local strains in the three-dimensional scaffolds to be compared with the physiological situation.

  14. TiNi shape memory alloys: effects of the fabrication route, the oxygen content and the zirconium or hafnium additions on the metallurgical characteristics and the thermomechanical properties; Alliages a memoires de forme de base TiNi: influence du mode de fabrication de la teneur en oxygene et de l`ajout de Zr ou Hf sur les caracteristiques metallurgiques et les proprietes mecaniques

    Energy Technology Data Exchange (ETDEWEB)

    Olier, P.

    1996-12-31

    In order to promote the development of Ti-Ni shape memory alloys, we have studied the correlation between the fabrication route, the chemical composition (O{sub 2} content, Zr or Hf additions), the metallurgical characteristics and the thermomechanical properties. A conventional sintering does not allow to obtain a homogeneous compound of pure Ti{sub 50}Ni{sub 50} alloy because of the occurrence of Kirkendall porosities which act as a diffusion barrier. An original process including combustion synthesis and hot-extrusion was successfully developed. Resulting products exhibit a smaller grain size (15-20{mu}m) and an enhanced workability in comparison with products obtained by arc-melting and subsequent hot rolling. The presence of oxygen in equiatomic Ti-Ni alloy induces the oxide precipitation of Ti{sub 4}Ni{sub 2}O{sub x} type (with x {<=} 1). The precipitated particle fraction is proportional to the oxygen nominal content of the alloy. We show that the decrease of the transformation temperatures is correlated with the decrease of Ti in solid solution due to Ti{sub 4}Ni{sub 2}O precipitation. Moreover, we find that a fine and homogenous oxide dispersion is suitable to decrease the grain size during hot rolling and to enhance to the one way shape memory properties. An increase of the typical transformation temperatures is obtained through of Zr or Hf (in substitution to Ti). But, an increase of the hardness is measured, and consequently the workability of the ternary alloys becomes reduced. However, it is worthwhile to point out that a Ti{sub 38}Ni{sub 50}Hf{sub 12} product obtained by arc melting and hot extrusion is able to fully recover an apparent plastic strain of more than 4% during tensile tests performed under special loading conditions. Such as behaviour is of great interest with respect to potential applications in a temperature range higher that 100 deg. C. (author). 105 refs.

  15. A novel method to prepare binary Ni-Fe compounds and ordered mesoporous carbon composite as a supercapacitor electrode

    Energy Technology Data Exchange (ETDEWEB)

    Feng, J.; Tang, B.; Zhao, J.; Liu, P.; Xu, J. [Shanghai Univ. of Engineering Science (China). College of Chemistry and Chemical Engineering

    2010-07-01

    Superapacitor electrodes with nickel/iron compounds and ordered mesoporous carbon (OMC) nanocomposites were fabricated using a incipient wetness impregnation and hydrothermal methods. The use of the nickel-iron compounds within the OMC framework resulted in a synergistic effect. Resistance was also improved. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses demonstrated that the host structure was preserved during the impregnation and hydrothermal procedures. Nano-sized metal compounds were formed within the mesopore system. Nitrogen adsorption and desorption isotherm measurements demonstrated mesoporosity for the host/guest composites.

  16. The effect of annealing on the mechanical properties and microstructural evolution of Ti-rich NiTi shape memory alloy

    Energy Technology Data Exchange (ETDEWEB)

    Tadayyon, Ghazal [Department of Metallurgical and Materials Engineering Faculty of Engineering, Ferdowsi University of Mashhad (Iran, Islamic Republic of); Centre for Research in Medical Devices (CURAM), National University of Ireland, Galway (Ireland); Mazinani, Mohammad, E-mail: mazinani@um.ac.ir [Department of Metallurgical and Materials Engineering Faculty of Engineering, Ferdowsi University of Mashhad (Iran, Islamic Republic of); Guo, Yina [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Zebarjad, Seyed Mojtaba [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Tofail, Syed A.M. [Materials and Surface Science Institute, University of Limerick, Limerick (Ireland); Biggs, Manus J. [Centre for Research in Medical Devices (CURAM), National University of Ireland, Galway (Ireland)

    2016-04-26

    An investigation was carried out into the influence of the annealing temperatures on the thermo-mechanical behavior of Ti-rich NiTi alloy with regard to transformation temperatures, mechanical properties at room temperature and microstructure evolution under deformation. It was found that annealing above the recrystallization temperature (600 °C) modulated the mechanical behavior of the alloy significantly. Based on tensile and DSC analysis, it was observed that by increasing the annealing temperature, the shape memory behavior of the alloys improved. Scanning and transmission electron microscopy were used to investigate the fracture surfaces and microstructural evolution of the NiTi samples after failure. Fractography revealed the brittle fracture area produced through the propagation of cleavage cracks; however, ductile fracture via nucleation growth and coalescence of micro-dimples in the martensitic phase at room temperature were also observed. During plastic deformation, the NiTi alloy was also observed to undergo a detwinning process, dislocation slip and the formation of submicrocrystalline grains, nanocrystallization and amorphous bands.

  17. Characteristics of the stress-induced formation of R-phase in ultrafine-grained NiTi shape memory wire

    International Nuclear Information System (INIS)

    Olbricht, J.; Yawny, A.; Pelegrina, J.L.; Eggeler, G.; Yardley, V.A.

    2013-01-01

    Highlights: •We investigated the stress-induced formation of R-phase in NiTi shape memory wires. •The R-phase related strains were isolated from the overall stress-strain-behavior. •The stress–strain characteristics of R-phase suggest a homogeneous transformation. •Thermography confirms the homogeneous R-phase formation in ultrafine-grained NiTi. -- Abstract: The transformation between the cubic B2 and monoclinic B19′ phases in ultrafine-grained pseudoelastic NiTi can occur as a two-step process involving the intermediate rhombohedral R-phase. Experimental work using differential scanning calorimetry, electrical resistance measurements and transmission electron microscopy has demonstrated the formation of this intermediate phase during thermal cycling and during mechanical loading. In the present paper, complementary mechanical and thermographic results are presented which allow to further assess the character of the stress-induced R-phase formation. The transformation from B2 to R-phase is demonstrated to occur homogeneously within the gauge length rather than via advancing Lüders-type transition regions as it is the case in the localized transformation from B2 or R-phase to B19′

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

    Science.gov (United States)

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

    2018-02-01

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

  19. Phase transformation, magnetic property and microstructure of Ni-Mn-Fe-Co-Ga ferromagnetic shape memory alloys

    International Nuclear Information System (INIS)

    Tsuchiya, K.; Sho, Y.; Kushima, T.; Todaka, Y.; Umemoto, M.

    2007-01-01

    Effects of addition of Fe and Co on the phase stability, magnetic property and microstructures were investigated for Ni-Mn-Ga. In Ni-Mn 21- x -Fe x -Ga 27 alloys, martensitic transformation temperatures decreased with increasing amount of Fe (x) up to 15 mol%, then slightly increased by the further addition. The crystal structure of martensite phase was 10 M for x 15 mol%. Relatively high martensite stability was obtained for Ni 52 -Mn 16- x -Fe x -Co 5 -Ga 27 alloys. The highest stability of the ferromagnetic martensite phase was achieved in Ni 52 -Mn 6 -Fe 10 -Co 5 -Ga 27 after aging at 773 K for 3.6 ks. Martensite structure was non-modulated 2 M in this series of alloys

  20. Thermoelectrical properties of the compounds ScM{sup VIII}Sb and YM{sup VIII}Sb (M{sup VIII} = Ni, Pd, Pt)

    Energy Technology Data Exchange (ETDEWEB)

    Oestreich, J; Probst, U; Richardt, F; Bucher, E [University of Konstanz, PO Box X916, D-78457 Konstanz (Germany)

    2003-02-05

    The research into new materials with good thermoelectric properties has revealed new compounds consisting of metallic elements (Bando Y, Suemitsu T, Takagi K, Tokushima H, Echizen Y, Katoh K, Umeo K, Maeda Y and Takabatake T 2000 J. Alloys Compounds 313 1-6, Ghelani N, Loo S, Chung D, Sportouch S, Nardi S, Kanatzidis M, Hogan T and Nolas G 2000 Mater. Res. Soc. 626 Z8.6.1). The half-Heusler compound ZrNiSn, in particular, shows promising thermoelectric properties and has been studied by many scientists during recent years (Uher C, Hu S, Yang J, Meisner G P and Morelli D T 1997 Proc. ICT'97: 16th Int. Conf. on Thermoelectrics pp 485-8, Romaka L P, Stadnyk Yu V, Goryn A M, Gorelenko Yu K and Skolozdra R V 1997 Proc. ICT'97: 16th Int. Conf. on Thermoelectrics pp 516-19, Hohl H, Ramirez A P, Goldmann C, Ernst G, Woelfing B and Bucher E 1998 J. Phys.: Condens. Matter 11 1697-709, Oestreich J, Kaefer W, Richardt F, Probst U and Bucher E 1999 Proc. 5th European Workshop on Thermoelectrics pp 192-5). In an effort to find new thermoelectric materials, the half-Heusler compounds of the groups ScM{sup VIII}Sb and YM{sup VIII}Sb (M{sup VIII} = Ni, Pd, Pt) were synthesized by arc melting and the thermoelectric properties were examined by standard characterization methods. Doping experiments showed that it is possible to change the electrical properties of the compounds while retaining the half-Heusler structure. Within the two groups, YPtSb showed the best thermoelectrical properties. At a temperature of 400 K the electrical conductivity of YPtSb is 748{omega}{sup -1} cm{sup -1} and the Seebeck coefficient is 116.3{mu}V K{sup -1}. The thermal conductivity at 400 K extrapolated using the Wiedemann-Franz law is 2.87 W K{sup -1} m{sup -1}. This leads to a dimensionless figure of merit of 0.14.

  1. Comparative Analysis of the Effects of Severe Plastic Deformation and Thermomechanical Training on the Functional Stability of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy

    Science.gov (United States)

    Atli, K. C.; Karaman, I.; Noebe, R. D.; Maier, H. J.

    2010-01-01

    We compare the effectiveness of a conventional thermomechanical training procedure and severe plastic deformation via equal channel angular extrusion to achieve improved functional stability in a Ti50.5Ni24.5Pd25 high-temperature shape memory alloy. Thermomechanical testing indicates that both methods result in enhanced shape memory characteristics, such as reduced irrecoverable strain and thermal hysteresis. The mechanisms responsible for the improvements are discussed in light of microstructural findings from transmission electron microscopy.

  2. Xenon focused ion beam in the shape memory alloys investigation – the case of NiTi and CoNiAl

    Czech Academy of Sciences Publication Activity Database

    Kopeček, Jaromír; Jurek, Karel; Kopecký, Vít; Klimša, Ladislav; Seiner, Hanuš; Sedlák, Petr; Landa, Michal; Dluhoš, J.; Petrenec, M.; Hladík, L.; Doupal, A.; Heczko, Oleg

    2014-01-01

    Roč. 20, Aug (2014), s. 335-336 ISSN 1431-9276 R&D Projects: GA ČR(CZ) GA14-03044S Institutional support: RVO:68378271 ; RVO:61388998 Keywords : scanning electron microscope * SEM * focused ion beam * FIB * xenon plasma focused ion beam * dual beam * shape memory alloy * SMA Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.877, year: 2014

  3. Microstructure and transformation behaviour of Ni75−XTiXPd25 high temperature shape memory alloys

    International Nuclear Information System (INIS)

    Ramaiah, K.V.; Saikrishna, C.N.; Gouthama; Bhaumik, S.K.

    2013-01-01

    Highlights: ► Partitioning of elements during solidification of cast NiTiPd results in cored microstructure. ► Homogenized alloys consists of NiTiPd matrix with Ti2(Ni,Pd) precipitates. ► Transformation temperatures of NiTiPd alloy is strongly dependent on Ti content. ► Transformation hysteresis was found to be relatively low, in the range 7–12 °C. ► Lower fraction of second phases and twinless/small twin ratio martensite led to low hysteresis. -- Abstract: The effect of composition on microstructure, transformation behaviour and thermal stability of cast and homogenized Ni 75−X Ti X Pd 25 alloys (X = 49.7, 50.0 and 50.3 at.%) were studied. Results showed significant partitioning of the alloying elements during solidification, resulting in cored microstructure in the cast alloys. The interdendritic regions were depleted in Pd and richer in Ni compared to dendritic regions. The interdendritic regions also showed presence of a thread-like Ti-rich second phase. The microstructure of the homogenized alloys consisted of NiTiPd matrix phase interspersed with Ti 2 (Ni,Pd) second phase precipitates. The precipitate phase was found to be rich in Ni and depleted in Pd. EPMA analysis showed that significant redistribution of Ni concentration in the matrix and the precipitate phase takes place during homogenization. X-ray diffraction study confirmed the matrix phase at room temperature to be of orthorhombic B19 structure. Study showed that the transformation temperatures of the alloys were strongly dependent on Ti content. The martensite finish temperature (M f ) of 157 °C for stoichiometric-Ti alloy increased to 179 °C and decreased to 105 °C for Ti-rich and Ti-lean alloys, respectively. Also, the alloys showed relatively low transformation hysteresis in the range 7–12 °C. TEM micrographs showed the presence of twinless/small twin ratio martensite which minimizes the interfacial energy and hence lower hysteresis. The transformation stability upon stress

  4. TEM study of structural and microstructural characteristics of a precipitate phase in Ni-rich Ni–Ti–Hf and Ni–Ti–Zr shape memory alloys

    International Nuclear Information System (INIS)

    Santamarta, R.; Arróyave, R.; Pons, J.; Evirgen, A.; Karaman, I.; Karaca, H.E.; Noebe, R.D.

    2013-01-01

    The precipitates formed after suitable thermal treatments in seven Ni-rich Ni–Ti–Hf and Ni–Ti–Zr high-temperature shape memory alloys have been investigated by conventional and high-resolution transmission electron microscopy. In both ternary systems, the precipitate coarsening kinetics become faster as the Ni and ternary element contents (Hf or Zr) of the bulk alloy are increased, in agreement with the precipitate composition measured by energy-dispersive X-ray microanalysis. The precipitate structure has been found to be the same in both Hf- and Zr-containing ternary alloys, and determined to be a superstructure of the B2 austenite phase, which arises from a recombination of the Hf/Zr and Ti atoms in their sublattice. Two different structural models for the precipitate phase were optimized using density functional theory methods. These calculations indicate that the energetics of the structure are not very sensitive to the atomic configuration of the Ti–Hf/Zr planes, thus significant configurational disorder due to entropic effects can be envisaged at high temperatures. The precipitates are fully coherent with the austenite B2 matrix; however, upon martensitic transformation, they lose some coherency with the B19′ matrix as a result of the transformation shear process in the surrounding matrix. The strain accommodation around the particles is much easier in the Ni–Ti–Zr-containing alloys than in the Ni–Ti–Hf system, which correlates well with the lower transformation strain and stiffness predicted for the Ni–Ti–Zr alloys. The B19′ martensite twinning modes observed in the studied Ni-rich ternary alloys are not changed by the new precipitated phase, being equivalent to those previously reported in Ni-poor ternary alloys

  5. Memories.

    Science.gov (United States)

    Brand, Judith, Ed.

    1998-01-01

    This theme issue of the journal "Exploring" covers the topic of "memories" and describes an exhibition at San Francisco's Exploratorium that ran from May 22, 1998 through January 1999 and that contained over 40 hands-on exhibits, demonstrations, artworks, images, sounds, smells, and tastes that demonstrated and depicted the biological,…

  6. Characterization and study of the behavior of wire Ti-Ni with shape memory effect enables manufacture of actuators; Estudo da caracterizacao e do comportamento de fios de Ti-Ni com efeito memoria de forma viabilizando fabricacao de atuadores

    Energy Technology Data Exchange (ETDEWEB)

    Pina, E.A.C.; Araujo Filho, O.O. de; Urtiga Filho, S.L.; Gonzalez, C.H., E-mail: kikipina@hotmail.co [Universidade Federal de Pernambuco (DEM/CTG/UFPE), Recife, PE (Brazil). Centro de Tecnologia e Geociencias. Dept. de Engenharia Mecanica

    2010-07-01

    This work aims to characterize the wire commercial Ti-Ni of 1.27 mm in diameter with shape memory effect for the development of helical springs with the function of sensor / actuator. After heat treatment, the transformation temperatures, the presence of precipitates, the degree of damping, maximum stress of rupture, modulus of elasticity, the presence of phase R, the behavior of the alloy under tension, will be analyzed and compared in each situation. For characterization we used several methods including: heat treatment, Differential Scanning Calorimetry (DSC), tensile, dynamic mechanical analysis (DMA), X-ray diffraction, thermomechanical cycling. The wires were cut into pieces and heat-treated at 400 deg C with variation of time in muffle furnaces and quenching in water at 25 deg C. (author)

  7. Electric quadrupole and magnetic dipole interactions at {sup 181}Ta impurity in Zr{sub 2}Ni{sub 7} intermetallic compound: Experiment and first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Dey, C.C., E-mail: chandicharan.dey@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Srivastava, S.K. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721302 (India)

    2013-10-15

    Electric quadrupole interactions at {sup 181}Ta impurity in the intermetallic compound Zr{sub 2}Ni{sub 7} have been studied by perturbed angular correlation technique. It has been found that there are two electric field gradients (EFG) at the {sup 181}Ta site due to two different crystalline configurations in Zr{sub 2}Ni{sub 7}, while contradictory results were reported from previous investigations. The values of EFG at room temperature have been found to be V{sub zz}=7.9×10{sup 17} V/cm{sup 2} and 7.1×10{sup 17} V/cm{sup 2} corresponding to present experimental values of quadrupole frequencies and asymmetry parameters for the two sites: ω{sub Q}{sup 1}=70.7(1) Mrad/s, η=0.28(1), δ=0.8(2)% (site fraction 84%) and ω{sub Q}{sup 2}=63(1) Mrad/s, η=0.35(5), δ∼0 (site fraction 9%). Electric field gradients and asymmetry parameters have been computed from the complementary first-principles density functional theory (DFT) to compare with present experimental results. Our calculated values of EFG are found to be in close agreement with the experimental results. No magnetic interactions in Zr{sub 2}Ni{sub 7} have been observed at 298 and 77 K which implies that there is no ferromagnetic ordering in this material down to 77 K. This observation is corroborated by theoretical calculations, wherein no magnetic moment or hyperfine field is found at any atomic site.

  8. Effect of Si substitution on structural, electronic and optical properties of YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Maurya, Dinesh Kumar; Saini, Sapan Mohan, E-mail: smsaini.phy@nitrr.ac.in

    2016-10-15

    We employed first principle calculations for investigation of structural, electronic and optical properties of YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds. These properties are studied first time on YNi{sub 4}Si-type DyNi{sub 5−x}Si{sub x} compounds. The exchange and correlation potential is treated by the Coulomb corrected local spin density approximation (LSDA+U) method for better accounting of the correlation between the 4f electrons. The optimized lattice constants and internal cell parameters are in agreement with the available data. Self consistence band structure calculations show that Ni-3d states remains in valance band and dominant below the E{sub F}, while Dy-5d and 4f states mainly contributes above Fermi Energy (E{sub F}) in DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) compounds. We also find that when silicon for nickel substitution takes place (DyNi{sub 4}Si), there is a gradual hybridization of Ni-3d and Si-3p states results, nickel moments decrease rapidly in agreement with the experiment. Optical spectra shows the main absorption peak around 4 eV depends on the substituent concentration and could be due to transition from hybridized band (Ni-3d and Si-3p), below E{sub F} to free Dy-4d states. Frequency-dependent refractive index, n(ω), and the extinction coefficient, k(ω), of DyNi{sub 5−x}Si{sub x} (x=0, 1, 2) are also calculated for the radiation up to 14 eV. - Highlights: • Calculated DOS revels that Ni-3d states are dominated below Fermi level (E{sub F}). • Spin down Dy-4f states show significant contribution to DOS above E{sub F.} • Nickel moments decrease rapidly with substitution of silicon for nickel (DyNi{sub 4}Si). • Most significant peak is found around 7eV in optical conductivity. • Nickel moments decrease rapidly with substitution of silicon for nickel (DyNi{sub 4}Si). • Peak indicates the possibility of transitions from Ni-3d states to empty spin down Dy-4f states.

  9. The formation of the two-way shape memory effect in rapidly quenched TiNiCu alloy under laser radiation

    International Nuclear Information System (INIS)

    Shelyakov, A V; Sitnikov, N N; Borodako, K A; Menushenkov, A P; Fominski, V Yu; Sheyfer, D V

    2015-01-01

    The effect of pulsed laser radiation (λ = 248 nm, τ = 20 ns) on structural properties and shape memory behavior of the rapidly quenched Ti 50 Ni 25 Cu 25 alloy ribbon was studied. The radiation energy density was varied from 2 to 20 mJ mm −2 . The samples were characterized by means of scanning electron microscopy, x-ray diffraction, microhardness measurements and shape memory bending tests. It was ascertained that the action of the laser radiation leads to the formation of a structural composite material due to amorphization or martensite modification in the surface layer of the ribbon. Two methods are proposed which allow one to generate the pronounced two-way shape memory effect (TWSME) in a local area of the ribbon by using only a single pulse of the laser radiation. With increasing energy density of laser treatment, the magnitude of the reversible angular displacement with realization of the TWSME increases. The developed techniques can be used for the creation of various micromechanical devices. (paper)

  10. Effect of milling duration on the evolution of shape memory properties in a powder processed Cu-Al-Ni-Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Mohit; Gupta, Gaurav K.; Shafeeq, Muhamed M.; Modi, Om P.; Prasad, Braj K. [CSIR - Advanced Materials and Processes Research Institute, Bhopal (India)

    2013-09-15

    The present work describes the effect of milling duration on the properties of a powder metallurgy processed Cu-Al-Ni-Ti shape memory alloy employing mechanical alloying. Powder mixtures milled for different durations were sintered in order to investigate the formation of solid solution and evolution of martensitic structure. The idea was to optimize the duration of milling (mechanical alloying) to obtain chemical homogeneity as well as shape memory properties in the processed material without undergoing extensive post homogenization treatment. The martensitic structure was noted to evolve in the powder mix milled for at least 16 hrs, whereas complete transformation to martensite occurred after milling for 40 hrs. Interestingly, the dissolution of alloying elements (to form the {beta} phase prior to the formation of martensite) was noted to complete partially only during mechanical alloying for 40 hrs and remaining during subsequent sintering for 1 hr. The hot pressed compacts of the powders milled for 40 hrs were chemically homogeneous and consisted of fully martensite phase, which is essential for the realization of shape memory properties. They also revealed almost 100% shape recovery at the applied pre-strain levels of 1 and 2%. (orig.)

  11. Evolution of macroscopic elastic moduli of martensitic polycrystalline NiTi and NiTiCu shape memory alloys with pseudoplastic straining

    Czech Academy of Sciences Publication Activity Database

    Thomasová, M.; Seiner, Hanuš; Sedlák, Petr; Frost, Miroslav; Ševčík, Martin; Szurman, I.; Kocich, R.; Drahokoupil, Jan; Šittner, Petr; Landa, Michal

    2017-01-01

    Roč. 123, January (2017), s. 146-156 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GP14-28306P; GA ČR GA14-15264S Institutional support: RVO:61388998 ; RVO:68378271 Keywords : shape memory alloys * polycrystals * elastic behavior Subject RIV: BM - Solid Matter Physics ; Magnetism; BM - Solid Matter Physics ; Magnetism (FZU-D) OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.); Condensed matter physics (including formerly solid state physics, supercond.) (FZU-D) Impact factor: 5.301, year: 2016

  12. Improvement of the shape memory effect of a Fe-Mn-Cr-Si-Ni by original thermomechanical treatments

    International Nuclear Information System (INIS)

    Federzoni, L.; Guenin, G.; Mantel, M.

    1993-01-01

    Among the shape memory alloys, Fe-based have real perspectives of industrial development. However, to acquire a good shape memory effect, these alloys must undergo a thermomechanical treatment. For applcation perspective this treatment must be the simpliest as possible. In this paper, two types of treatment have been performed, based of the fact that : - the formation of the martensite ε, responsible for the shape memory effect, is sensitive to the microstructure - its reversibility is the best as possible if the austenite is previously hardened by a deformation at high temperature. (orig.)

  13. Feasibility of Shape-Memory Ni/Ti Alloy Wire Containing Tube Elevators for Transcrestal Detaching Maxillary Sinus Mucosa: Ex Vivo Study

    Directory of Open Access Journals (Sweden)

    Yanfeng Li

    2016-12-01

    Full Text Available Background: Osteotome sinus floor elevation is a less invasive approach to augment an insufficient alveolar bone at the posterior maxilla for dental implantation. However, this approach has some limitations due to the lack of sinus lift tools available for clinical use and the small transcrestal access to the maxillary sinus floor. We recently invented shape-memory Ni/Ti alloy wire containing tube elevators for transcrestal detaching maxillary sinus mucosa, and developed goat ex vivo models for direct visualizing the effectiveness of detaching sinus mucosa in real time during transcrestal maxillary sinus floor elevation. Methods: We evaluated our invented elevators, namely elevator 012 and elevator 014, for their effectiveness for transcrestal detaching maxillary sinus mucosa using the goat ex vivo models. We measured the length of sinus mucosa detached in mesial and distal directions or buccal and palatal directions, and the space volume created by detaching maxillary sinus mucosa in mesial, distal, buccal and palatal directions using the invented elevators. Results: Elevator 012 had a shape-memory Ni/Ti alloy wire with a diameter of 0.012 inch, while elevator 014 had its shape-memory Ni/Ti alloy wire with a diameter of 0.014 inch. Elevator 012 could detach the goat maxillary sinus mucosa in the mesial or distal direction for 12.1±4.3 mm, while in the buccal or palatal direction for 12.5±6.7 mm. The elevator 014 could detach the goat maxillary sinus mucosa for 23.0±4.9 mm in the mesial or distal direction, and for 19.0±8.1 mm in the buccal or palatal direction. An average space volume of 1.7936±0.2079 ml was created after detaching the goat maxillay sinus mucosa in both mesial/distal direction and buccal/palatal direction using elevator 012; while the average space volume created using elevator 014 was 1.8764±0.2366 ml. Conclusion: Both two newly invented tube elevators could effectively detach the maxillary sinus mucosa on the goat ex

  14. Feasibility of Shape-Memory Ni/Ti Alloy Wire Containing Tube Elevators for Transcrestal Detaching Maxillary Sinus Mucosa: Ex Vivo Study.

    Science.gov (United States)

    Li, Yanfeng; Wang, Fuli; Hu, Pin; Fan, Jiadong; Han, Yishi; Liu, Bin; Liu, Tao; Yang, Chunhao; Gu, Xiangmin

    2016-01-01

    Osteotome sinus floor elevation is a less invasive approach to augment an insufficient alveolar bone at the posterior maxilla for dental implantation. However, this approach has some limitations due to the lack of sinus lift tools available for clinical use and the small transcrestal access to the maxillary sinus floor. We recently invented shape-memory Ni/Ti alloy wire containing tube elevators for transcrestal detaching maxillary sinus mucosa, and developed goat ex vivo models for direct visualizing the effectiveness of detaching sinus mucosa in real time during transcrestal maxillary sinus floor elevation. We evaluated our invented elevators, namely elevator 012 and elevator 014, for their effectiveness for transcrestal detaching maxillary sinus mucosa using the goat ex vivo models. We measured the length of sinus mucosa detached in mesial and distal directions or buccal and palatal directions, and the space volume created by detaching maxillary sinus mucosa in mesial, distal, buccal and palatal directions using the invented elevators. Elevator 012 had a shape-memory Ni/Ti alloy wire with a diameter of 0.012 inch, while elevator 014 had its shape-memory Ni/Ti alloy wire with a diameter of 0.014 inch. Elevator 012 could detach the goat maxillary sinus mucosa in the mesial or distal direction for 12.1±4.3 mm, while in the buccal or palatal direction for 12.5±6.7 mm. The elevator 014 could detach the goat maxillary sinus mucosa for 23.0±4.9 mm in the mesial or distal direction, and for 19.0±8.1 mm in the buccal or palatal direction. An average space volume of 1.7936±0.2079 ml was created after detaching the goat maxillay sinus mucosa in both mesial/distal direction and buccal/palatal direction using elevator 012; while the average space volume created using elevator 014 was 1.8764±0.2366 ml. Both two newly invented tube elevators could effectively detach the maxillary sinus mucosa on the goat ex vivo sinus models. Moreover, elevator 014 has advantages over

  15. Surface Characteristics of Machined NiTi Shape Memory Alloy: The Effects of Cryogenic Cooling and Preheating Conditions

    Science.gov (United States)

    Kaynak, Y.; Huang, B.; Karaca, H. E.; Jawahir, I. S.

    2017-07-01

    This experimental study focuses on the phase state and phase transformation response of the surface and subsurface of machined NiTi alloys. X-ray diffraction (XRD) analysis and differential scanning calorimeter techniques were utilized to measure the phase state and the transformation response of machined specimens, respectively. Specimens were machined under dry machining at ambient temperature, preheated conditions, and cryogenic cooling conditions at various cutting speeds. The findings from this research demonstrate that cryogenic machining substantially alters austenite finish temperature of martensitic NiTi alloy. Austenite finish ( A f) temperature shows more than 25 percent increase resulting from cryogenic machining compared with austenite finish temperature of as-received NiTi. Dry and preheated conditions do not substantially alter austenite finish temperature. XRD analysis shows that distinctive transformation from martensite to austenite occurs during machining process in all three conditions. Complete transformation from martensite to austenite is observed in dry cutting at all selected cutting speeds.

  16. Damping characteristics of a Ti40.5Ni49.5Zr10 shape memory alloy

    International Nuclear Information System (INIS)

    Hsieh, S.F.; Wu, S.K.

    2005-01-01

    Ti 40.5 Ni 49.5 Zr 10 alloy undergoes B2-bar B19' martensitic transformation. Damping capacities of B19' and B2 phases of this alloy are lower than those of Ti 51 Ni 49 alloy due to Zr atoms solid-soluted hardening. Transformation temperatures of this alloy decrease, but transformation peak heights Q max -1 increase with increasing aging time at 300 o C due to the formation of finer (001) M twins for specimens aged longer. The Q max -1 peaks of the slightly cold-rolled Ti 40.5 Ni 49.5 Zr 10 alloy are higher than those of the as-annealed alloy, which may be because the thinner twins are induced by small deformation

  17. Crystallographic features of the martensitic transformation and their impact on variant organization in the intermetallic compound Ni50Mn38Sb12 studied by SEM/EBSD.

    Science.gov (United States)

    Zhang, Chunyang; Zhang, Yudong; Esling, Claude; Zhao, Xiang; Zuo, Liang

    2017-09-01

    The mechanical and magnetic properties of Ni-Mn-Sb intermetallic compounds are closely related to the martensitic transformation and martensite variant organization. However, studies of these issues are very limited. Thus, a thorough crystallographic investigation of the martensitic transformation orientation relationship (OR), the transformation deformation and their impact on the variant organization of an Ni 50 Mn 38 Sb 12 alloy using scanning electron microscopy/electron backscatter diffraction (SEM/EBSD) was conducted in this work. It is shown that the martensite variants are hierarchically organized into plates, each possessing four distinct twin-related variants, and the plates into plate colonies, each containing four distinct plates delimited by compatible and incompatible plate interfaces. Such a characteristic organization is produced by the martensitic transformation. It is revealed that the transformation obeys the Pitsch relation ({0[Formula: see text]} A // {2[Formula: see text]} M and 〈0[Formula: see text]1〉 A // 〈[Formula: see text]2〉 M ; the subscripts A and M refer to austenite and martensite, respectively). The type I twinning plane K 1 of the intra-plate variants and the compatible plate interface plane correspond to the respective orientation relationship planes {0[Formula: see text]} A and {0[Formula: see text]} A of austenite. The three {0[Formula: see text]} A planes possessed by each pair of compatible plates, one corresponding to the compatible plate interface and the other two to the variants in the two plates, are interrelated by 60° and belong to a single 〈11[Formula: see text]〉 A axis zone. The {0[Formula: see text]} A planes representing the two pairs of compatible plates in each plate colony belong to two 〈11[Formula: see text]〉 A axis zones having one {0[Formula: see text]} A plane in common. This common plane defines the compatible plate interfaces of the two pairs of plates. The transformation strains to form the

  18. Explosive device of conduit using Ti Ni alloy

    Directory of Open Access Journals (Sweden)

    A. Yu. Kolobov

    2014-01-01

    Full Text Available Presently, materials have been developed which are capable at changing temperate to return significant inelastic deformations, exhibit rubber-like elasticity, convert heat into mechanical work, etc. The aggregate of these effects is usually called the shape memory effect.At present a great number of compounds and alloys with a shape memory effect has been known.These are alloys based on titanium nickelide (TiNi, copper-based alloys (Cu-Al, Cu-Sn, Cu-Al-Ni, Cu-Zn-Si, etc., gold and silver (Ag-Cd, Au-Ag-Cd, Au-Cd-Cu, Au-Zn-Cu, etc., manganese (Mn-Cr, Fe-Cu, Mn-Cu-Ni, Mn-Cu-Zr, Mn-Ni, etc., iron (Fe-Mn, Fe-Ni, Fe-Al, etc., and other compounds.The alloys based on titanium nickelide (nitinol are the most widely used.Alloys with shape memory effect find various applications in engineering and medicine, namely connecting devices, actuators, transformable design, multipurpose medical implants, etc.There is a task of breaking fuel conduit during separating the spacecraft from the rocket in space technology.The paper examines the procedure for design calculation of the separating device of conduit with the use of Ti-Ni alloy. This device can be used instead of the pyro-knives.The device contains two semi-rings from Ti-Ni alloy. In the place of break on the conduit an annular radius groove is made.At a temperature of martensite passage the semi-rings undergo deformation and in the strained state are set in the device. With heating to the temperature of the austenitic passage of bushing macro-deformation the energy stored by the nitinol bushing is great enough to break the conduit on the neck.The procedures of design calculation and response time of device are given.

  19. Stress-induced martensite variant reorientation in magnetic shape memory Ni-Mn-Ga single crystal studied by neutron diffraction

    Czech Academy of Sciences Publication Activity Database

    Molnar, P.; Šittner, P.; Lukáš, Petr; Hannula, S.-P.; Heczko, O.

    2008-01-01

    Roč. 17, č. 3 (2008), 035014/1-035014/5 ISSN 0964-1726 Institutional research plan: CEZ:AV0Z10480505 Keywords : NI2MNGA * Transformation * Alloy Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.743, year: 2008

  20. Thin film Heusler compounds manganese nickel gallium

    Science.gov (United States)

    Jenkins, Catherine Ann

    Multiferroic Heusler compounds Mn3--xNi xGa (x=0,1,2) have a tetragonal unit cell that can variously be used for magneto-mechanically coupled shape memory ( x=1,2) and spin-mechanical applications (x=0). The first fabrication of fully epitaxial thin films of these and electronically related compounds by sputtering is discussed. Traditional and custom lab characterization of the magnetic and temperature driven multiferroic behavior is augmented by more detailed synchrotron-based high energy photoemission spectroscopic techniques to describe the atomic and electronic structure. Integration of the MnNi2Ga magnetic shape memory compound in microwave patch antennas and active free-standing structures represents a fraction of the available and promising applications for these compounds. Prototype magnetic tunnel junctions are demonstrated by Mn3Ga electrodes with perpendicular anisotropy for spin torque transfer memory structures. The main body of the work concentrates on the definition and exploration of the material series Mn3--xNi xGa (x=0,1,2) and the relevant multiferroic phenomena exhibited as a function of preparation and external stimuli. Engineering results on each x=0,1,2 are presented with device prototypes where relevant. In the appendices the process of the materials design undertaken with the goal of developing new ternary intermetallics with enhanced properties is presented with a full exploration of the road from band structure calculations to device implementation. Cobalt based compounds in single crystal and nanoparticle form are fabricated with an eye to developing the production methods for new cobalt- and iron-based magnetic shape memory compounds for device applications in different forms. Mn2CoSn, a compound isolectronic and with similar atomic ordering to Mn2NiGa is experimentally determined to be a nearly half-metallic ferromagnet in contrast to the metallic ferrimagnetism in the parent compound. High energy photoemission spectroscopy is shown to