Conventional Shape Memory Alloys Research Articles

Effects of iron oxide and carbon nanotube contents on mechanical properties and shape memory behavior of biocompatible and biodegradable shape memory polymers

AbstractThe shape memory polymers (SMPs) is a potential alternative material for conventional shape memory alloys (SMAs) in various fields. Previous studies have focused on the application of SMPs materials as an alternative to SMAs. However, considering problems such as the poor mechanical properties, its application has been limited. This study developed a biodegradable, magnetically responsive SMPs material that can be used for medical implants with shape memory behavior under magnetic force and improved mechanical properties by adding nanoparticles. Moreover, effect of the added nanoparticle was investigated due to contents ratio. Nanocomposite was synthesized with polycaprolactone which has shape memory properties, Fe3O4 that generates heat under magnetic field, and carbon nanotubes with reinforcing effect. The morphology analysis confirmed the homogeneous dispersion of the Fe3O4/Carbon‐nanotubes (CNTs) in polymer matrix. The tensile test shows that tensile strength (14.9–17.6 MPa) increased when Fe3O4 (0–20 wt%) was included and that it did not increase significantly when CNTs (0–0.8 wt%) were included. The shape memory test result confirmed that developed composite had a shape memory under a magnetic field. It was confirmed that even if Fe3O4 was incorporated into polycaprolactone, did not lose its exothermic properties under magnetic field. The developed polymer showed high shape memory ratio (91%–98%) in all the nanoparticle content rates. With regard to biodegradability, weight loss occurred over time in the phosphate‐buffered saline solution. Therefore, the biocompatible, biodegradable, magnetic response shape memory polymer developed in this study might applied to various medical implant as advanced shape memory materials.

Seismic displacement response of SDOF systems with SMA slip friction dampers

Owing to superelastic behavior, shape memory alloy (SMA) has been widely utilized to develop self-centering damping devices. Recently, the authors developed a novel SMA damper, i.e. the SMA slip friction (SMASF) damper. The cyclic behavior of the SMASF damper not only depends on the hysteresis shape factors of SMA bars, but also on the coefficient of kinetic friction and the slope of the friction plates. Hence, the basic working mechanism of the SMASF damper is different from that of conventional SMA dampers. In the early work, the features of the SMASF damper have been revealed by static cyclic loading tests. However, the seismic displacement responses of this novel damper remain unknown. To this end, this paper initiates with a brief introduction of the damper, including the configuration, working mechanism, and testing results. And then, extensive seismic analyses based on single-degree-of-freedom systems were conducted. Based on the constant-strength ductility demand spectra, the displacement responses of the SMASF damper were understood through the comparisons with conventional SMA damper and friction damper. A wide range of fundamental periods, strength capacities and seismic intensity levels were considered. Further, parametric analysis was conducted to assess the effect of the hysteresis shape factors of SMA bars and the coefficient of kinetic friction and the slope of the friction plates. This study also sheds light on the force-based seismic design method for this damper.

A Novel Cooling Design for an Agonistic–Antagonistic SMA Tendon-Driven Actuator

Shape memory alloys (SMAs) exhibit a unique property that undergoes deformation in response to temperature variation. This characteristic can be utilized via the application of a filiform SMA wire to tendon-driven robotic actuators for biomimetic joint movements. However, due to the inefficiencies in heat dissipation, conventional SMA tendon-driven actuators are characterized by their lower relaxation speeds than other actuators. This paper proposes a novel cooling design for an SMA tendon-driven actuator using thin-fin heat sinks based on a multi-layer wrapped SMA tendon design. In addition, the electric circuit and the controller are refined. Prototype devices are constructed to validate the performance of SMA-based actuators under PID control. The results indicate that the proposed design exceeds previous models in terms of relaxation performance by up to 5.8 times while also being able to stabilize at a target angle within 0.5 s under control.

A novel response-amplified shape memory alloy-based damper: Theory, experiment and numerical simulation

The energy dissipation capacity of shape memory alloy (SMA) dampers can be effectively improved owing to the success of response amplification technology. However, conventional response-amplified SMA dampers for building structures still face a risk of failure during extremely rare earthquake events. In this study, a novel response-amplified SMA damper (RASD) is proposed with the advantages of fully exploiting the energy dissipation characteristics of SMA materials and avoiding material failure. First, the components, configuration, and working principles of the proposed damper were described. Subsequently, a restoring-force model of the RASD was established, and its accuracy was verified through cyclic loading tests. Finally, seismic performance mitigation of a single-degree-of-freedom (SDOF) system under different hazard levels was conducted to evaluate the effectiveness and advantages of the proposed RASD quantitatively. The results reveal that the RASD has a good force amplification effect and excellent damping enhancement effect and thus conspicuously mitigates the seismic response of the SDOF system. In particular, the proposed RASD can effectively reduce the force and displacement demand of SMA materials without the risk of SMA failure, while significantly mitigating the structural response.

A shape memory alloy implant can be an effective surgical treatment in the atlantoaxial joint stabilization using rabbits as substitutes for toy-breed dogs.

To investigate the feasibility of using shape memory alloy (SMA) implants for atlantoaxial joint stabilization using a rabbit model as a substitute for canines. 20 rabbit cadavers. We prepared rabbit cadavers from the middle of the skull to the third cervical vertebra. The vertebral body and canal sizes of the atlas and axis were compared using CT data from rabbits, normal dogs, and dogs with atlantoaxial instability (AAI) to assess the feasibility of using rabbits as substitutes for toy-breed dogs. The shape memory alloy (SMA) implants were designed to stabilize the atlantoaxial joint without compromising the spinal canal passage for safety and were classified into SMA-1 and SMA-2 based on their design. To evaluate the strength, the ventrodorsal force was measured with atlantoaxial ligaments intact, after removing the ligaments, and after applying conventional wire or SMA implants to stabilize the atlantoaxial joint. The time taken for implant application was measured. No significant difference in vertebral body size of the atlas and axis was observed. A significant difference in vertebral canal size was observed between the animals. In biomechanical testing, the SMA-2 implant provided more stabilization, while the SMA-1 implant had lower strength than the conventional method using wires. The application time of wire was the longest, while that of SMA-1 was the shortest. SMA implants provide comparable strength and demonstrate superior efficacy compared to conventional dorsal wire fixation of atlantoaxial stabilization. Therefore, SMA implants can be an effective surgical option for AAI.

Influence of thermomechanical treatment on the shape memory effect and pseudoelasticity behavior of conventional and additive manufactured Fe–Mn–Si–Cr–Ni-(V,C) shape memory alloys

This study evaluated the influence of heat treatment and thermomechanical training on the microstructural evolution and mechanical characteristics of conventional and additive-manufactured FeMnSi-based shape memory alloys. The conventional samples were produced by casting and rolling. The additive-manufactured samples were manufactured using the laser powder bed fusion (L-PBF) technique. Both specimens were subjected to the same heat treatment and thermomechanical training. The heat treatment involved solution annealing at 1050 °C for 2 h and aging at 750 °C for 6 h, and the thermomechanical training concluded with a 4% elongation at ambient temperature followed by annealing at 250 °C for 15 min. This training cycle was repeated four times for each sample after heat treatment. The heat treatment improved the pseudoelasticity and shape memory effect of the samples. Although training further enhanced the pseudoelasticity, it also reduced the shape memory effect. Thermomechanical training led to the formation of a large number of stacking faults, which facilitated the inverse phase transformation of martensite (ε) to austenite (γ) during unloading, resulting in improved pseudoelasticity. The heat-treated additive-manufactured samples showed the highest total recovery strain owing to the pseudoelasticity and shape memory effect. This characteristic could be due to the smaller grain size and higher volume fraction of precipitates. The precipitates and grain refinement improved the conditions for partial dislocation motion by increasing the back stresses on the martensite tip.

Improving the functional stability of TiNi-based shape memory alloy by multi-principal element design

This study investigated the evolutions of the superelasticity and elastocaloric effect of a multi-principal element Ti40Zr10Ni40Co5Cu5 strain glass alloy during 3001 cyclic compressions. The results were compared with a conventional solution-treated Ti49Ni51 shape memory alloy. The Ti40Zr10Ni40Co5Cu5 strain glass alloy exhibited a higher hardness, lower residual strain, and lower dislocation density due to multi-principal element solid solution strengthening and strong lattice distortion. Furthermore, it showed stable critical stress and elastocaloric cooling temperature drop during the cyclic test, and the values were maintained at 90.9 and 83.3 % after 3001 cycles, respectively. Digital image correlation analyses showed that the Ti40Zr10Ni40Co5Cu5 strain glass alloy exhibited a more homogeneous martensitic transformation behavior instead of the localized Lüders-type one. This feature originated from the high density of atomic defects, which in turn improved the temperature uniformity of the material during elastocaloric cooling. Experimental results demonstrated that the multi-principal element design method effectively suppressed dislocation slip and thus improved the functional stability and transformation homogeneity of the shape memory alloy, so such alloys are potential candidates for solid-state refrigerants.

Processing parameters and martensitic phase transformation relationships in near defect-free additively manufactured NiTiHf high temperature shape memory alloys

Additive Manufacturing (AM) has quickly emerged as a promising technology to manufacture Shape Memory Alloy (SMA)-based components of complex geometries. 3D-printed High Temperature SMAs (HT-SMAs) components can enable applications that demand operating temperatures well beyond conventional NiTi SMAs. Here, a detailed printability assessment of NiTiHf HT-SMAs fabricated using laser powder bed fusion (LPBF) AM is conducted for the first time. Specifically, the regions associated with lack of fusion, keyholing, and balling regimes are quantitatively classified through an efficient printability assessment framework. Nearly porosity-free specimens are achieved from the predicted good printable region. The effects of key processing parameters (laser power, scanning speed, and hatch spacing) on the microstructure variation and phase transformation characteristics are studied systematically. A positive correlation is observed between the transformation temperatures and volumetric energy density (EV). Beyond a critical EV of 100 J/mm3, the transformation temperatures become insensitive to further increases in EV. At identical or similar energy density levels, the individual change of laser power, scanning speed, or hatch spacing alters the transformation behavior to a certain extent. It is hypothesized that to a large extent, this behavior is due to the effects that processing conditions have on the differential evaporation of Ni from the melt pool. A model connecting thermal histories, scanning strategy and chemistry changes is found to be consistent with this hypothesis. It is shown that the transformation temperatures in AM NiTiHf HT-SMAs can be varied over a range of more than 160 °C by controlling Ni evaporation through altering processing parameters.

High‐Speed Antagonistic Shape Memory Actuator for High Ambient Temperatures

This work presents the development of an innovative shape memory alloy (SMA) actuator principle, which allows high‐speed switching cycles through the decoupling of antagonistically arranged SMA wires. Being optimized for the use at high ambient temperatures up to 65 °C, a possible application area is the active venting of injection molds where it can be used to expel air, which is trapped during the injection mold process. The patented actuator principle is based on a decoupled agonist–antagonist SMA‐spring system and allows a high‐speed closing movement by a compact and lightweight design. Another innovation compared to conventional antagonistic SMA actuator systems is the integrated fail‐safe mechanism, which guarantees a defined closed state in case of power failure. Subsequently, in the motivation the need for active venting valves for injection molding is first described. Second, the novel actuator principle is introduced, and the development of an electronics concept is discussed. Finally, the design process, assembly, and validation of two iterations of the actuator prototype are presented. The final prototype validation measurements showcase high performance by valve strokes of 1 mm within 100 ms at ambient temperature of 65 °C.

Molecular dynamics simulations of ultralow hysteretic behavior in super-elastic shape memory alloys

Shape memory alloys (SMAs) that exhibit superelasticity with large recoverable strain and small hysteresis are in demand for practical applications, although their synthesis remains a challenge. We introduce metastable engineering to dope conventional SMA solid-solution atoms of relatively high concentration with "weak" local lattice distortion to realize ultralow hysteretic superelasticity. Large-scale molecular dynamic (MD) simulations of NiTi-based SMAs are performed to demonstrate how the presence of 2 ∼ 4 at.% Nb dopants lead to a stress-induced transition from a metastable pretransitional state to a strain-glass state. This is facilitated by a macroscopically homogeneous and continuous phase transformation in the course of superelastic loading and unloading. This spinodal decomposition-like phase transformation process endows SMAs with anhysteretic superelasticity that is insensitive to loading direction and grain size (below 15 nm). These findings show promise of achieving ultralow hysteretic superelasticity with large recoverable strain for SMAs.

A two-scale thermo-mechanically coupled model for anomalous martensite transformation and elastocaloric switching effect of shape memory alloy

Conventional shape memory alloys (SMAs) exhibit an approximately linear relationship between the critical stresses of martensite transformation (MT) and ambient temperature (Clausius-Clapeyron relationship). Meanwhile, depending on the sign of entropy difference between the parent and martensite phases, these alloys behavior either a conventional or an inverse elastocaloric effect which originates from the latent heat release/absorption during stress-induced MT. Recently, MT with a non-monotonic Clausius-Clapeyron relationship (denotes as anomalous MT) and an elastocaloric switching effect (changes from the inverse elastocaloric effect at relatively low temperature to the conventional elastocaloric effect at relatively high temperature) were reported in CoCr-based Heusler-type SMAs. In this paper, to understand and quantitatively describe these new phenomena, a two-scale thermo-mechanically coupled constitutive model is constructed. In the mesoscopic scale, the fine twinned structure and the potential correspondent variant pairs of martensite phase are analyzed based on the crystallographic symmetry and the geometrically nonlinear theory of MT. The classical Debye's model is employed to describe the lattice and electronic heat capacities of the parent and martensite phases; while, a Monte Carlo simulation for the three-dimensional (3D) Ising's model is performed and a scaling law for the magnetic heat capacity of parent phase is proposed. Then, a new constitutive model is established based on the fundamental laws of irreversible thermodynamics to describe the non-isothermal stress-induced MT between parent and martensite phases. To consider the thermo-mechanical interactions between the parent phase and correspondent martensite variant pairs, each variant pair is regarded as an inhomogeneous inclusion with a mobile interface and embedded in the parent phase. With the help of interfacial operator, the thermodynamic driving force of MT is derived from the constructed Helmholtz free energy and dissipative inequality. Internal heat generation originated from the thermo-elasticity, inelastic deformation dissipation and latent heat is derived from the conservation law of energy. In the macroscopic scale, the thermo-mechanical response of SMA specimen is obtained by solving the equations of force balance, deformation compatibility, and thermodynamic equilibrium through the full-field calculation and mean-field approximation. Finally, the proposed model is verified by comparing the predictions with the experiments. It can be found that the anomalous MT and elastocaloric switching effect of CoCrAlSi SMA can be well captured by the proposed model.

Residual displacements of reinforced concrete walls detailed with conventional steel and shape memory alloy rebars

Modern reinforced concrete design codes can generally achieve the primary performance level of no collapse in the event of a rare to very rare earthquake. However, recent seismic events have shown that permanent damage and deformations of buildings prevent the structure from being serviceable, imposing high costs associated with repairs or demolition. Shape memory alloys have the ability to recover large strains upon removal of stress. Thus, replacing conventional steel with superelastic alloy rebars in the boundary ends of reinforced concrete walls has the potential to reduce residual seismic displacements for these types of buildings. This research paper investigates the lateral residual displacement of reinforced concrete walls detailed with conventional steel and shape memory alloy bars as a function of the in-plane drift. Namely, the force-displacement hysteresis of a large dataset of experimental walls with conventional steel are used to study the residual displacement as a function of several key design parameters. A state-of-the-art finite element modelling program is then used to investigate the residual displacements of walls detailed with shape memory alloy bars, and a parametric study is undertaken to investigate the influence of residual displacements of these types of walls. Most of the walls reinforced with shape memory alloys achieved residual displacements less than the permissible limit at large drift levels. The axial load was found to help suppress the residual displacements of walls with increasing drift. The curvatures were found to be distributed over a limited height at the base that was equivalent to the length of the shape memory alloy bar used. Plastic hinge analysis expressions are adapted to estimate the operational displacement of reinforced concrete walls with shape memory alloys.

Mechanical behavior of cycled shape memory alloy

Shape memory alloys (SMA) are often used in many industrial, medical and automotive fields due to the ability to recover the initial shape caused by external loads. This aspect is due to the variations of the microstructure that may depend on thermal and/or mechanical causes. So far, many models have been developed in order to describe the mechanical behaviour of SMA but most of them do not take into account the real microstructure.In this work a conventional equiatomic NiTi SMA has been investigated in both terms of microstructure evaluation and mechanical cycling behaviour up to degradation the memory ability, which has obtained at around 100 cycles. The cycling behaviour has been investigated and a model has been proposed to predict the mechanical behaviour and the ability to recover the initial microstructure.The damaged alloy has been investigated in terms of fracture surface analysis obtained by conventional tensile tests after 1, 50 and 100 cycles.

Investigations of mechanical properties and deformation behaviors of the Cr modified Ti–Au shape memory alloys

In view of the population aging issues, the functional materials, Ti–Au–Cr shape memory alloys (SMAs), have been explored in this study for the crucial biomaterial applications. This ternary system was chosen for solving the hypersensitivity problem in the conventional SMAs containing Ni and also for its high X–ray contrast, which is an essential requirement in medical applications. Physical metallurgy methods were utilized for the specimen preparation and the fundamental properties and functional performances were also evaluated. Cold–workability was greatly improved with the Cr addition. The parent β–phase was stabilized by 4.5 at.% Cr alloying concentration, while the discrimination of the α′–martensite phase and the α′′–martensite phase at low Cr addition concentrations was clarified. Lattice parameters and the deformation strains were further calculated based on the results of the X–ray diffraction analysis. Most of the specimens possessed shape recovery upon heating, while the Ti–4.0Au–5.5Cr alloy showed an almost perfect shape recovery rate of 96.7%. Pseudoelastic behavior was observed in most of the alloys. The austenite transformation temperatures were determined by the step–by–step heating processes.

Pseudoelasticity of SrNi2P2 Micropillar via Double Lattice Collapse and Expansion.

The maximum recoverable strain of most crystalline solids is less than 1% because plastic deformation or fracture usually occurs at a small strain. In this work, we show that a SrNi2P2 micropillar exhibits pseudoelasticity with a large maximum recoverable strain of ∼14% under uniaxial compression via unique reversible structural transformation, double lattice collapse-expansion that is repeatable under cyclic loading. Its high yield strength (∼3.8 ± 0.5 GPa) and large maximum recoverable strain bring out the ultrahigh modulus of resilience (∼146 ± 19 MJ/m3), a few orders of magnitude higher than that of most engineering materials. The double lattice collapse-expansion mechanism shows stress-strain behaviors similar to that of conventional shape-memory alloys, such as hysteresis and thermo-mechanical actuation, even though the structural changes involved are completely different. Our work suggests that the discovery of a new class of high-performance ThCr2Si2-structured materials will open new research opportunities in the field of pseudoelasticity.

Temperature Dependent Stress–Strain Behavior and Martensite Stabilization in Magnetic Shape Memory Ni51.1Fe16.4Ga26.3Co6.2 Single Crystal

The superelastic properties and stress-induced martensite (SIM) stabilization have been studied in a shape memory Ni51.1Fe16.4Ga26.3Co6.2 single crystal. The single crystal, characterized by a thermally induced forward martensitic transformation temperature around 56 °C in the initial state, has been submitted to compression mechanical testing at different temperatures well above, near and below the martensitic transformation (MT). After each mechanical test, the characteristic MT temperatures and the transformation enthalpy have been monitored by means of differential scanning calorimetry. At temperatures below MT, the stress–strain (σ–ε) curves show a large strain, around 6.0%, resulting from the detwinning process in the martensitic microstructure, which remains accumulated after unloading in the detwinned state of the sample as a typical behavior of the shape memory alloys (SMAs). After just two “σ–ε + heating” cycles the accumulation of strain was not observed any more indicating the formation of a two-way shape memory effect which consists in a spontaneous recovery of the aforementioned detwinned state of the sample during its cooling across the forward MT. Whereas the thermally induced shape recovery in conventional SMAs occurs at the fixed value of the reverse MT temperature, the heating DSC curves of the mechanically deformed martensite in the present work show a burst-like calorimetric peak at the reverse MT arising at temperatures essentially higher than the thermally activated one. This behavior is the result of the SIM stabilization effect. After a short thermal aging in the stress-free state, this effect almost disappears, showing a slight impact on the MT characteristic temperatures and the enthalpy. At temperatures higher than the transformation one, the SIM is not stabilized, as the mechanically induced martensite fully retransforms into austenite after the unloading. From the σ–ε curves, the critical stress, σc, as well as the values of Young’s moduli of martensite and austenite are determined showing linear dependences on the temperature with a slope of 3.6 MPa/°C.

Novel prestressing applications in civil engineering structures enabled by Fe[sbnd]Mn[sbnd]Al[sbnd]Ni shape memory alloys

The present study reports on the feasibility of using Fe-Mn-Al-Ni shape memory alloys as prestressing elements in civil engineering. Polycrystalline Fe-Mn-Al-Ni specimens were prestrained and subsequently heated up under constant strain in order to evaluate the prestressing potential of the material. Due to the formation of precipitates as a function of both, maximum heating temperature and dwell time, the prestress level of the material can be tailored. Moreover, in oligocrystalline specimens prestress losses, e.g., due to shrinkage and creep of concrete, can be impeded by changing the functional properties from shape memory effect to superelasticity. Based on the results presented it can be concluded that the Fe-Mn-Al-Ni system is a promising alternative to conventional shape memory alloys used for prestressing applications eventually enabling novel and innovative applications in numerous civil engineering structures by utilizing the well-defined evolution of precipitates during activation.

A Double Shape Memory Alloy Damper for Structural Vibration Control

Shape memory alloy (SMA) dampers are widely investigated passive control systems for structural vibration mitigation. However, the damping robustness of conventional austenite SMA dampers may be affected by environmental temperature. In this study, an innovative double SMA damper (DSD) system is presented to improve the temperature robustness of the SMA dampers. In the proposed system, double SMA hysteretic elements with different phase transition temperatures are arranged in parallel, where the SMA element with lower transition temperature behaves as austenite under room temperature, and the other with higher transition temperature behaves as martensite. To study the vibration control effect, both single-degree-of-freedom (SDOF) and multiple-degree-of-freedom (MDOF) structures with DSD systems are employed. The thermal and mechanical behaviors of the SMA elements and the working principle of DSD are also introduced. Thereon, the equivalent linearization method for SMA’s output force and the motion-governing equations for SDOF structure with DSD are derived. Moreover, parametric studies are conducted to investigate the performance of the proposed DSD system in both frequency and time domains. Also, numerical analysis for the MDOF structure with DSD systems is carried out to illustrate the trend in response reduction with an increasing number of degrees of freedom. The analytical results show that the DSD can mitigate the structural seismic response more effectively than the conventional one with acceptable residual deformation, and is capable of delaying the degradation of SMA’s energy dissipation capacity. Less SMA material is required for the proposed DSD to fulfill the same mitigation requirement, and it is suitable for general applications for temperature robustness.

Numerical Simulation of Cu-Al-Mn Endodontic Instruments under Bending and Torsional Conditions

This study focuses on the development of endodontic instruments manufactured from Cu-Al-Mn shape memory alloys (SMAs) which are more economical and easier to process as compared to conventional NiTi SMAs. Finite element analysis of three different numerical instruments was performed using material parameters of Cu-Al-Mn and conventional superelastic NiTi. Flexural and torsional stiffness of these instruments with the resulting von Mises stresses were evaluated under bending and twisting based on the ISO 3630-1 specification. All the studied Cu-Al-Mn endodontic files exhibited superior flexibility and lower reaction stresses as compared to NiTi endodontic files during bending, resulting from their low elastic modulus and starting stress value for the martensitic transformation. However, low torsional stiffness and high von Mises stress values related with the high angular displacement were obtained for Cu-Al-Mn endodontic instruments under torsional loading. Geometric differences of different models have been an important factor in adjusting the stiffness of endodontic instruments. Consequently, it was determined that Cu-Al-Mn SMA could be used as an alternative material in the manufacture of endodontic files that have large cross-sectional area and moment of inertia.

High temperature superelasticity realized in equiatomic Ti-Ni conventional shape memory alloy by severe cold rolling

Great interests on high temperature shape memory alloys (HTSMAs) are recently raised, driven primarily by the aerospace and automotive industries, for their potential to serve as solid state actuators at high temperatures over 373 K. Near equiatomic Ti-Ni conventional SMAs, as the most applied SMA system, were considered to possess appreciable shape memory effect and superelasticity only below 373 K, which owes to low martensitic transformation temperatures. Here we utilized the martensite stabilization effect and successfully expanded the viable zone of B19′ (monoclinic) martensite to 616 K in a 35% cold-rolled Ti-50Ni (CR35) SMA. After a training cycle, it exhibited quasi-linear superelasticity of narrow hysteresis, ~3% superelastic strain and high strength over 1.2 GPa in a wide temperature range up to 483 K. It is the first exploration of high temperature superelasticity associated with the stabilized martensite. Using transmission electron microscopy and in-situ heating/tensile synchrotron X-ray diffraction, we reveal the origin of martensite stabilization and the underlying mechanisms of unique superelasticity in the CR35. Our work provides an attractively facile approach to realize high temperature superelasticity in Ti-Ni conventional SMAs, as well as in other kinds of SMAs, for precise actuation within an expanded range of working temperature and stress.