Origin of high strength, low modulus superelasticity in nanowire-shape memory alloy composites

Zhang, Xudong; Zong, Hongxiang; Cui, Lishan; Fan, Xueling; Ding, Xiangdong; Sun, Jun

doi:10.1038/srep46360

Cited by 13 publications

(9 citation statements)

References 44 publications

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“…According Shahinpoor and Schneider 32 , there are three types of superelastic behavior in SMA work-hardened: superelasticity, linear superelasticity (when martensite is cold worked by about 10%), and nonlinear superelasticity (for which transformation occurs with strain at practically constant stress, presenting narrow hysteresis and small residual strain). Interestingly, the Ni-Ti SMA helical springs manufactured by ICC exhibit a quasi-linear superelasticity, recovering almost all the imposed strains, with narrow stress hysteresis, which is similar to the results of other previous studies 33,34 . Probably, this behavior results from the interaction between the nucleation of martensite in the Ni-Ti matrix phase (austenite) and residual stresses in precipitates during martensitic transformation 35,36 .…”

Section: Tensile Testssupporting

confidence: 89%

Thermomechanical Characterization of Superelastic Ni-Ti SMA Helical Extension Springs Manufactured by Investment Casting

2019

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Shape memory alloy (SMA) helical springs are special mechanical parts that require a previous evaluation of its behavior for application. Therefore, in this paper thermal and mechanical behaviour of superelastic Ni-Ti SMA helical extension springs manufactured by investment casting (IC) are evaluated. Phase transformation temperatures were measured by Electrical Resistance as a function of Temperature (ERT) and Differential Scanning Calorimetry (DSC). Tensile tests were carried out within strain and temperatures ranges. The pitch angle and stiffness of each spring were determined. Results demonstrated that Ni-Ti SMA helical springs produced by IC presented phase transformation corresponding to the superelastic effect (SE). The reversible deformations under tensile test were of the order of 70%. The mechanical behavior as function of temperature revealed a linear relationship between maximum force and spring temperature.

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Section: Tensile Testssupporting

confidence: 89%

Thermomechanical Characterization of Superelastic Ni-Ti SMA Helical Extension Springs Manufactured by Investment Casting

2019

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“…With a planar view (Figure 7(A)), the bright areas in Figure 7 [61] It was reported that the interaction between the nucleation of martensite in the TiNi matrix and the residual stress in Nb precipitates can induce spatially inhomogeneous initiation and propagation of martensite, causing continuous phase transformation resulting in the quasi-linear superelasticity. [62] In this picture, during the interaction the precipitates would bear the overall load in elastic deformation giving rise to the narrow hysteresis and the TiNi matrix behaves as load transfer increases with rising residual stress. [62][63][64][65][66] A criterion based on the large aspect ratio and the volume fraction of precipitates, and applied pre-strain is proposed to achieve the quasi-linear superelasticity in general.…”

Section: Resultsmentioning

confidence: 99%

“…[62] In this picture, during the interaction the precipitates would bear the overall load in elastic deformation giving rise to the narrow hysteresis and the TiNi matrix behaves as load transfer increases with rising residual stress. [62][63][64][65][66] A criterion based on the large aspect ratio and the volume fraction of precipitates, and applied pre-strain is proposed to achieve the quasi-linear superelasticity in general. [62] We believe a similar interaction is taking place here.…”

Section: Resultsmentioning

confidence: 99%

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Elastocaloric cooling of additive manufactured shape memory alloys with large latent heat

Hou¹,

Simsek²,

Stasak³

et al. 2017

J. Phys. D: Appl. Phys.

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The stress-induced martensitic phase transformation of shape memory alloys (SMAs) is the basis for elastocaloric cooling. Here we employ additive manufacturing to fabricate TiNi SMAs, and demonstrate compressive elastocaloric cooling in the TiNi rods with transformation latent heat as large as 20 J g −1 . Adiabatic compression on as-fabricated TiNi displays cooling DT as high as −7.5 °C with recoverable superelastic strain up to 5 %. Unlike conventional SMAs, additive manufactured TiNi SMAs exhibit linear superelasticity with narrow hysteresis in stress-strain curves under both adiabatic and isothermal conditions. Microstructurally, we find that there are Ti 2 Ni precipitates typically one micron in size with a large aspect ratio enclosing the TiNi matrix. A stress transfer mechanism between reversible phase transformation in the TiNi matrix and mechanical deformation in Ti 2 Ni precipitates is believed to be the origin of the unique superelasticity behavior. Abstract:The stress-induced martensitic phase transformation of shape memory alloys (SMAs) is the basis for elastocaloric cooling. Here we employ additive manufacturing to fabricate TiNi SMAs, and demonstrate compressive elastocaloric cooling in the TiNi rods with transformation latent heat as large as 20 J g −1 . Adiabatic compression on as-fabricated TiNi displays cooling ∆T as high as −7.5 °C with recoverable superelastic strain up to 5 %. Unlike conventional SMAs, additive manufactured TiNi SMAs exhibit linear superelasticity with narrow hysteresis in stress-strain curves under both adiabatic and isothermal conditions. Microstructurally, we find that there are Ti2Ni precipitates typically one micron in size with a large aspect ratio enclosing the TiNi matrix.A stress transfer mechanism between reversible phase transformation in the TiNi matrix and mechanical deformation in Ti2Ni precipitates is believed to be the origin of the unique superelasticity behavior.

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“…1b). The motivation for the choice of such a nanostructure is the advancements in fabrication techniques of composites and their various associated phenomena [41][42] [43]. The Ti-Nb nanocomposite has four microscopic features related to the macroscopic mechanical properties, namely the Nb concentration (CNb) of the matrix (MNb) and nanofillers (FNb), volume fraction of nanofillers (VF), and number of nanofillers (NF).…”

Section: Model and Proceduresmentioning

confidence: 99%

Linear-superelastic Ti-Nb nanocomposite alloys with ultralow modulus via high-throughput phase-field design and machine learning

Zhu

Wei

et al. 2021

npj Comput Mater

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The optimal design of shape memory alloys (SMAs) with specific properties is crucial for the innovative application in advanced technologies. Herein, inspired by the recently proposed design concept of concentration modulation, we explore martensitic transformation (MT) in and design the mechanical properties of Ti-Nb nanocomposites by combining high-throughput phase-field simulations and machine learning (ML) approaches. Systematic phase-field simulations generate data of the mechanical properties for various nanocomposites constructed by four macroscopic degrees of freedom. An ML-assisted strategy is adopted to perform multiobjective optimization of the mechanical properties, through which promising nanocomposite configurations are prescreened for the next set of phase-field simulations. The ML-guided simulations discover an optimized nanocomposite, composed of Nb-rich matrix and Nb-lean nanofillers, that exhibits a combination of mechanical properties, including ultralow modulus, linear super-elasticity, and near-hysteresis-free in a loading-unloading cycle. The exceptional mechanical properties in the nanocomposite originate from optimized continuous MT rather than a sharp first-order transition, which is common in typical SMAs. This work demonstrates the great potential of ML-guided phase-field simulations in the design of advanced materials with extraordinary properties.

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Origin of high strength, low modulus superelasticity in nanowire-shape memory alloy composites

Cited by 13 publications

References 44 publications

Thermomechanical Characterization of Superelastic Ni-Ti SMA Helical Extension Springs Manufactured by Investment Casting

Thermomechanical Characterization of Superelastic Ni-Ti SMA Helical Extension Springs Manufactured by Investment Casting

Elastocaloric cooling of additive manufactured shape memory alloys with large latent heat

Linear-superelastic Ti-Nb nanocomposite alloys with ultralow modulus via high-throughput phase-field design and machine learning

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