Shape memory strains and temperatures in the extreme

Şehitoğlu, Hüseyin; Patriarca, L.; Wu, Y.

doi:10.1016/j.cossms.2016.06.005

Cited by 35 publications

(7 citation statements)

References 76 publications

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“…Since the superelastic functional properties of NiTi wires are affected by the microstructure and test temperature, one needs to investigate both (or at least to be sure that 9,10,11,12,13,14,15). As far as we are aware of, this is the first ever dataset of this kind published in the literature.…”

Section: Temperature and Microstructure Dependence Of Tensile Deformamentioning

confidence: 99%

“…However, the superelastic NiTi wires exhibit instability of cyclic stress-strain response and related functional and structural fatigue, which represents serious problems for many promising engineering applications. It was linked to the transformation-plasticity coupling in the literature [3][4][5][6][7][8][9][10][11]. In this respect, tensile tests until rupture on NiTi wires have become of interest again.…”

Section: Introductionmentioning

confidence: 99%

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Tensile Deformation of Superelastic NiTi Wires in Wide Temperature and Microstructure Ranges

Chen

Tyc

Molnárová

et al. 2018

Shap. Mem. Superelasticity

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Superelastic NiTi wires were prepared from a single cold worked wire by various electropulse heat treatments. The wires having a wide range of virgin microstructures were subjected to tensile tests until rupture and cyclic superelastic tensile testing in a wide temperature range. The results were complemented by TEM observation of lattice defects created by superelastic cycling. It appeared that the yield stress depends significantly on the wire microstructure and less on the test temperature. The upper plateau stress varies with the microstructure through its effect on the Ms temperature and increases with increasing temperature in accord with the Clausius-Clapeyron equation up to a maximum temperature characteristic for each microstructure. The upper plateau strains exhibit pronounced maxima (12-18%) at test temperatures and microstructures (pulse times), at which the upper plateau stress approaches the yield stress. The instability of cyclic superelastic deformation was found to be inversely related to the difference between the yield stress and upper plateau stress. Cyclic deformation introduces dislocation slip in the microstructure of the cycled wire from the 3rd cycle and promotes formation of {114} austenite twins upon later cycling. These observations were explained by the activation of deformation twinning in oriented martensite and the stress induced B2 ) B19 0 ) B2 T martensitic transformation in specific range of microstructures and temperatures. The ductility of the tested wires was observed to vary stepwise with microstructure from * 13 up to * 55% and gradually decreased with temperature increasing above 100°C.

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Section: Temperature and Microstructure Dependence Of Tensile Deformamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tensile Deformation of Superelastic NiTi Wires in Wide Temperature and Microstructure Ranges

Chen

Tyc

Molnárová

et al. 2018

Shap. Mem. Superelasticity

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“…Numerous alloy systems have been developed and proposed so far. Up to now, ternary Ni-Ti-Hf is the most promising HT-SMA, since substantial progress has been made recently with respect to processing and functional performance [3,4]. Still, costs are quite high due to the high amounts of Hafnium [1].…”

Section: Introductionmentioning

confidence: 99%

Excellent superelasticity in a Co-Ni-Ga high-temperature shape memory alloy processed by directed energy deposition

Lauhoff

Sommer

Vollmer

et al. 2020

Materials Research Letters

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A Co-Ni-Ga high-temperature shape memory alloy has been additively manufactured by directed energy deposition. Due to the highly anisotropic microstructure, i.e. columnar grains featuring a strong near-001 texture in build direction, the as-built material is characterized by a very low degree of constraints and, thus, shows excellent superelasticity without conducting a post-process heat treatment. As characterized by in situ deformation testing and post-mortem microstructural analysis, additive manufacturing employing directed energy deposition seems to be highly promising for processing of shape memory alloys, which often suffer difficult workability. IMPACT STATEMENTThe present work establishes a new pathway towards realization of high performance shape memory alloys by additive manufacturing and, thus, will stimulate further research in this field directed towards application.

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“…The maximum operating temperature of commercially available Ti–Ni shape memory alloys is limited to around 350 K due to their low martensitic and reverse transformation temperatures [1,2,3]. In recent years, there have been strong demands for actuators operating at higher temperatures above 373 K (100 °C); therefore, there have been substantial research efforts to develop high-temperature shape memory alloys [4,5,6,7,8,9,10].…”

Section: Introductionmentioning

confidence: 99%

Effect of Stoichiometry on Shape Memory Properties and Functional Stability of Ti–Ni–Pd Alloys

et al. 2019

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Ti–Ni–Pd shape memory alloys are promising candidates for high-temperature actuators operating at above 373 K. One of the key issues in developing high-temperature shape memory alloys is the degradation of shape memory properties and dimensional stabilities because plastic deformation becomes more pronounced at higher working temperature ranges. In this study, the effect of the Ti:(Ni + Pd) atomic ratio in TixNi70−xPd30 alloys with Ti content in the range from 49 at.% to 52 at.% on the martensitic transformation temperatures, microstructures and shape memory properties during thermal cycling under constant stresses were investigated. The martensitic transformation temperatures decreased with increasing or decreasing Ti content from the stoichiometric composition. In both Ti-rich and Ti-lean alloys, the transformation temperatures decreased during thermal cycling and the degree of decrease in the transformation temperatures became more pronounced as the composition of the alloy departed from the stoichiometric composition. Ti2Pd and P phases were formed during thermal cycling in Ti-rich and Ti-lean alloys, respectively. Both Ti-rich and Ti-lean alloys exhibited superior dimensional stabilities and excellent shape memory properties with higher recovery ratio and larger work output during thermal cycling under constant stresses when compared with the alloys with near-stoichiometric composition.

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Shape memory strains and temperatures in the extreme

Cited by 35 publications

References 76 publications

Tensile Deformation of Superelastic NiTi Wires in Wide Temperature and Microstructure Ranges

Tensile Deformation of Superelastic NiTi Wires in Wide Temperature and Microstructure Ranges

Excellent superelasticity in a Co-Ni-Ga high-temperature shape memory alloy processed by directed energy deposition

Effect of Stoichiometry on Shape Memory Properties and Functional Stability of Ti–Ni–Pd Alloys

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