The functionalities of Ni–Ti alloys subjected to different deformation treatments are studied. A critical stress corresponding to the onset of degradation of the functional properties were determined; it was found that this stress is about twice as low as the yield stress. The efficiency coefficients of virtual thermodynamic machines with a working body made of the investigated materials were calculated and compared with the efficiency of a Carnot engine based on the same materials; the ideality factor has been calculated under the condition of actuating at stresses no higher than critical ones. It has been established that, at the single actuation, the highest ideality factor (9.7%) is characteristic of a material consisting of bars 20 to 5 mm in diameter obtained by warm forging at 350°C. It has been determined that, at discontinuous operation under stresses lower than the critical ones by a factor of 1.2, the ideality factor is 7.4–7.7% for alloys subjected to hot forging or equal channel angular pressing combined with warm forging.

A test machine has been designed for studying the thermomechanical properties of shape-memory-alloy microwires in a temperature range from −190 to +270°C, under mechanical stresses as high as 2000 MPa, and with deformations of up to 50%. The operation of the test machine is based on the method of sample stretching at a variable temperature and a constant load. The elongation of the sample is measured by an optical displacement sensor. The machine was tested on microwires made from the well-known Ni49.8Ti50.2 alloy with the shape memory effect. Using the machine, it is possible to investigate the functional properties of microwire samples with a shape memory effect, which are promising for applications in microsystem engineering, nanotechnology, and medical technology.

Recently the new scheme of layered composite with shape memory effect (SME) for thermal and magnetic actuation was suggested and proved to demonstrate the reversible actuation on micro- and nanoscale. The principles of magnetic field induced martensitic transition (MFIMT) and magnetic field controlled shape memory effect (MFCSME) have the advantages of magnetic-field-controlled actuation at constant temperature, extremely small size of an actuator and compatibility with modern nanotechnologies. The present paper is devoted to experimental study of MFCSME in two ferromagnetic Heusler alloys Ni54Mn21Ga25 and Ni50Mn41.2In8.8 with positive and negative shift of the martensitic transition temperature in a magnetic field. The three points bending device for dilatometric tests of plate-like samples of the alloys was designed and placed in the field of Bitter coil magnet. The bending deformations versus temperature were measured at various magnetic fields up to 10 T and at mechanical stresses up to 45 MPa. The temperature shifts of thermoelastic martensitic phase transition were found to be 0.55 K/T and -0.95 K/T for Ni54Mn21Ga25 and Ni50Mn41.2 In-8.(8) respectively. For direct MFCSME study the dependences of the bending deformation on magnetic fields up to 14 T were also obtained at constant temperatures for these alloys. Practically complete recoverable deformation of 0.2% due to MFIMT was obtained at 14 T in Ni54Mn21Ga25 alloy in temperature range 316-318 K and stress 8.6 MPa. The new variant of the layered functional composite actuator scheme based on the alloys with MFCSME is suggested. The proposed functional composite combines the layers of the alloys with positive and negative temperature shifts of martensitic transition temperature in magnetic field. It is argued that this combination of the alloys can improve the performance of the composite actuators driven by MFCSME, particularly, it can provide higher generated force, actuation stroke, sensitivity to magnetic field and frequency of actuation.

An experimental test machine for studying of the thermomechanical properties of shape-memory alloys in the temperature range from −130 to +300°C under mechanical stresses of up to 2000 MPa and the maximum bending deformation of a sample of up to 20% is described. The principle of operation of the test machine is based on three-point bending of a sample at a variable temperature and a constant load. The deflection of the sample is measured by an optical displacement transducer, which determines the high accuracy and reliability of the results. The apparatus was tested using samples of the Ni49.8Ti50.2 shape-memory alloy.

AbstractThe pulse response of the actuator based on rapidly quenched Ti_2NiCu alloy with a thermoelastic martensitic transformation and the shape memory effect is studied experimentally. The mechanical response of the actuator cooled by running water is preserved when the duration of the excitation (activating) electric pulses decreases to 2 ms. High-speed activation is accompanied by a delay in the mechanical pulse in comparison with the excitation electric pulse. The minimum duration of the mechanical pulse, taking into account the delay, was 8 ms, which corresponds to a frequency of 125 Hz with periodic activation. Estimates show that the delay time includes both the time of mechanical inertia and the time of thermal inertia associated with heat transfer. The possible limitation of the rate of activation due to kinetic phenomena during the thermoelastic martensitic transition is evaluated.

The properties of nanorods made of high-energy-gap Zn x Mg1 – xO semiconductors are experimentally investigated using the new system of 3D manipulation of individual nanospecimens. The technology used to prepare Zn x Mg1 – xO nanorods via gas-phase deposition on a substrate, the process whereby individual nanorods are selected by means of nanocomposite tweezers with the shape-memory effect in the vacuum chamber of a two-beam scanning microscope, and the results obtained when their structure and morphology are experimentally studied using transmission electron spectroscopy are described. The prospects that nanophotonic, nanosensorial, and nanoelectronic devices can be fabricated from Zn x Mg1 – xO nanorods via the new nanomanipulation technique are discussed.

The pulse response of the actuator based on rapidly quenched Ti 2 NiCu alloy with a thermoelastic martensitic transformation and the shape memory effect is studied experimentally. The mechanical response of the actuator cooled by running water is preserved when the duration of the excitation (activating) electric pulses decreases to 2 ms. High-speed activation is accompanied by a delay in the mechanical pulse in comparison with the excitation electric pulse. The minimum duration of the mechanical pulse, taking into account the delay, was 8 ms, which corresponds to a frequency of 125 Hz with periodic activation. Estimates show that the delay time includes both the time of mechanical inertia and the time of thermal inertia associated with heat transfer. The possible limitation of the rate of activation due to kinetic phenomena during the thermoelastic martensitic transition is evaluated.

AbstractSamples of microactuators are made of a bimorph composite of Ti_2NiCu alloy with a thermoelastic martensitic transition and the shape memory effect, and their response rate is investigated. The active layer of the composite actuator is a layer of the rapidly quenched Ti_2NiCu alloy, pseudoplastically prestretched, and an amorphous layer of the same alloy is used as an elastic layer. Typical sizes of the microactuator are 30 × 2 × 2 μm. The controlled amplitude of the displacement of the microactuator tip is approximately 1 μm. The response rate of the microactuator was investigated by scanning electron microscopy. Activation of the microactuator was achieved by heating when electric pulses were passed through it. Full activation of the microactuator at frequencies up to 1 kHz was demonstrated; partial activation was observed at frequencies up to 8 kHz. The possibility of operating the device in a self-oscillating mode at frequencies of the order of 100 kHz is demonstrated.

The forces of interaction between objects on the nanoscale greatly affect the process of 3D nanomapulation. The work is devoted to an experimental study of the sticking force of nanoobjects (ZnO nanowhiskers) to a micro nanomanipulator (composite nanotweezers Ti2NiCu with shape memory effect (SME). Surface interaction is very important, at the both stages of capture, and detachment from the substrate of the nanoobject, and when the object is freed from capture and fixed to a new substrate. The interaction was observed in a SEM equipped with a Kleindiek micromanipulator. The nanotweezers were fixed on the tip of tungsten microwire. It approached and removed from the ZnO nanowhisker. The critical distance at which the attraction begins to appear was determined for the metal surface of the nanotweezers and for the surface covered with thin ZnO film.

Samples of microactuators are made of a bimorph composite of Ti2NiCu alloy with a thermoelastic martensitic transition and the shape memory effect, and their response rate is investigated. The active layer of the composite actuator is a layer of the rapidly quenched Ti2NiCu alloy, pseudoplastically prestretched, and an amorphous layer of the same alloy is used as an elastic layer. Typical sizes of the microactuator are 30 × 2 × 2 μm. The controlled amplitude of the displacement of the microactuator tip is approximately 1 μm. The response rate of the microactuator was investigated by scanning electron microscopy. Activation of the microactuator was achieved by heating when electric pulses were passed through it. Full activation of the microactuator at frequencies up to 1 kHz was demonstrated; partial activation was observed at frequencies up to 8 kHz. The possibility of operating the device in a self-oscillating mode at frequencies of the order of 100 kHz is demonstrated.

TEM measurements are used to experimentally study thermoelastic martensite transformation in Ti2NiCu tapered plates. The martensite phase is observed at room temperature in the Ti2NiCu alloy when the plate thickness decreases to, at least, 80 nm, and the austenite phase is observed at smaller thicknesses. It is shown that the temperature of thermoelastic martensite transition in the Ti2NiCu alloy decreases with a decrease in the thickness of the plate, the transition is blocked at a thickness of less than 20 nm, and a hysteresis dependence is observed. Possible physical and technological reasons for blocking of the martensite phase transition on nanoscale and fundamental limitations on the sizes of micromechanical devices based on the shape-memory Ti2NiCu alloy are considered.

New promising functional materials—amorphous-crystalline fast-quenched Ti2NiCu alloys exhibiting the shape memory effect (SME)—are studied. A method for annealing amorphous alloys by electric current pulses is proposed. This method allows one to obtain the needed degree of crystallinity. It is demonstrated that a microcrystalline structure with spherical grains exists in amorphous-crystalline samples. These grains increase in size from 150 nm to 3.2 μm as the degree of annealing increases. The SME is not observed in nontreated samples and is clearly manifested in completely annealed samples. A two-way SME and a trend toward lowering of the martensitic transition temperature are observed in partially annealed samples.

The shape memory effect (SME) in alloys with a thermoelastic martensite transition opens unique opportunities for the creation of miniature mechanical devices. The SME has been studied in layered composite microstructures consisting of a Ti2NiCu alloy and platinum. It occurs upon a decrease in the active layer thickness at least to 80 nm. Some physical and technological restrictions on the minimum size of a material with SME are discussed.

Samples of thermally controlled shape memory alloy (SMA) composite nanotweezers based on bilayered structures Ti 2 NiCu/Pt with dimensions (0.8–30)×(0.1–10)×(0.07–2)μm have been developed. Each of these composites could be used to create the smallest miniature devices to date for micro- and nanomechanics, fluidics, electronics, medicine and S&A technologies. It was found that the reversible deformation of the composite created by FIB milling is greater than 1 % when the thickness of SMA layer varies from 1μm to 100 nm. The new system of nanotweezers actuation by application of electric current is proposed and theoretical modeling of the new system was done. Experimental tests of the new control system of nanotweezers have been performed. The actuation of nanotweezers in a full cycle (open — close — open) was demonstrated with frequency as high as 1 kHz. Further increase of frequency causes the decrease of bending deformation of nanotweezers. Nevertheless, even at 100 kHz self-oscillation have been detected directly under constant voltage apply. We have demonstrated 3D manipulation of 30 nm single carbon nanotube, stack of graphene layers, viskers of different materials and even mosquito's hair.