Mechanisms for phase transformation induced slip in shape memory alloy micro-crystals

Paranjape, Harshad M.; Bowers, M.L.; Mills, Michael J.; Anderson, Peter M.

doi:10.1016/j.actamat.2017.04.066

Cited by 79 publications

(20 citation statements)

References 27 publications

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“…There is dislocation contrast in the austenite matrix as well as in the austenite twins. These dislocations are different from the {011}/\ 100 [ slip dislocations in austenite we observed earlier in the 16 ms NiTi wire after 10 superelastic cycles at room temperature [26] or which others reported [27,28]. It is thus possible that the deformation twinning in martensite involves dislocation slip in martensite.…”

Section: Mechanisms Of the Stress Induced B2 ) B19 0 ) B2 T Martensitic Transformationcontrasting

confidence: 73%

“…9). These experimental results, particularly to the {114} austenite twins in the microstructure of deformed wires, can be hardly explained considering the conventional dislocation slip based mechanisms of functional fatigue of NiTi proposed in the state of the art articles on this topic in the literature [3,[27][28][29][30][31].…”

Section: Mechanisms Of the Stress Induced B2 ) B19 0 ) B2 T Martensitic Transformationmentioning

confidence: 91%

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B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

Šittner

Heller

Sedlák

et al. 2019

Shap. Mem. Superelasticity

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Deformation of superelastic NiTi wire with tailored microstructure was investigated in tensile loadingunloading tests up to the end of the stress plateau in wide temperature range from room temperature up to 200°C. Lattice defects left in the microstructure of deformed wires were investigated by transmission electron microscopy. Tensile deformation is localized up to the highest test temperatures, even if practically no martensite phase exists in the wire at the end of the stress plateau. In tensile tests at elevated temperatures around 100°C, at which the upper plateau stress approaches the yield stress for plastic deformation of martensite, upper plateau strains become unusually long, transformation strains become unrecoverable and deformation bands containing {114} austenite twins appear in the microstructure of deformed wires. These observations were rationalized by assuming activity of B2 ) B19 0 ) B2 T martensitic transformation into the austenite twins representing a new mechanism of plastic deformation of NiTi, additional to the dislocation slip in austenite and/or martensite. It is claimed that this transformation becomes activated in any thermomechanical load in which the oriented B19 0 martensite is exposed to high stress at high temperatures, as e.g., during shape setting or actuator cycling at high applied stress.Keywords Materials Á Stress-induced martensitic transformation Á Superelasticity Á Twinning This article is an invited submission to Shape Memory and Superelasticity selected from presentations at the Shape Memory and Superelastic Technology Conference and Exposition (SMST2019) held May 13-17, 2019 at The Bodensee Forum in Konstanz, Germany, and has been expanded from the original presentation.

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Section: Mechanisms Of the Stress Induced B2 ) B19 0 ) B2 T Martensitic Transformationcontrasting

confidence: 73%

Section: Mechanisms Of the Stress Induced B2 ) B19 0 ) B2 T Martensitic Transformationmentioning

confidence: 91%

B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

Šittner

Heller

Sedlák

et al. 2019

Shap. Mem. Superelasticity

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“…The plastic strain originating from cyclic martensitic transformation is transformation-induced plasticity (Kang et al, 2009). Since transformation-induced plasticity is most likely to accumulate at austenitemartensite interface or its closest vicinity owing to lattice mismatch (Bowers et al, 2014;Hamilton et al, 2004;Paranjape et al, 2016Paranjape et al, , 2017Simon et al, 2010), austenite-martensite interface is deemed as the only origin of transformation-induced plasticity…”

Section: Rate Of Overall Inelastic Strain and Stress Inhomogeneitymentioning

confidence: 99%

“…As shown in equation ( 75), r can hardly affect the transformation criterion if h equals to 1. So, the influence of r is studied by setting h to be 1.1, spanning r within a commonly located range, that is, between 0.05 and 1 (Bowers et al, 2014;Norfleet et al, 2009;Paranjape et al, 2017;Yu et al, 2015b), and fixing other parameters unchanged. As can be seen in Figure 8, transformation hardening modulus and saturated residual strain increase while temperature amplitude decreases with increasing r. Hence, setting r at 0.25 presents a moderate and representative evaluation on thermomechanical coupling and superelasticity degeneration of NiTi.…”

Section: Effect Of Interaction Parameter and Shape Parametermentioning

confidence: 99%

A microstructure-based constitutive model accounting for rate dependence of superelastic NiTi alloy under cyclic deformation

Xiao

Zhang

Lei

2019

Journal of Intelligent Material Systems and Structures

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In this work, a micromechanical constitutive model based on single crystal is proposed to account for the rate dependence and functional degradation of superelastic NiTi. Correspondence variant pair is treated as ellipsoid inclusion embedded in austenite matrix, and the stress distribution is obtained through Mori–Tanaka homogenization. Two inelastic mechanisms, that is, martensitic transformation and transformation-induced plasticity, are taken into consideration. Slipping is modeled to originate from austenite–martensite interface and is transferred between austenite and martensite. The heat equilibrium equation and thermodynamic driving force are deduced from the first law of thermodynamics and Clausius–Duhem inequality, respectively. Via the introduction of dominant <111> texture and Taylor approximation, the single crystal model is extended to polycrystalline version. The calibration and numerical implementation procedures for the model are systemized. The effects of key prescribed material parameters are discussed. Simulation results are validated against the experimental data. It is found that simulated thermomechanical responses agree with experimental observations reasonably.

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“…During service, the NiTi devices normally undergo cyclic phase transformation between a B2 structured austenite (A) phase and a B19' structured martensite (M) phase [2]. The B2/B19' interface mismatch during transformation leads to generation of dislocations and plastic strain [4][5][6][7][8][9][10][11][12]. The irreversible plastic strain accumulates during cyclic phase transformation, resulting in degradation of functional properties (i.e.…”

mentioning

confidence: 99%

Improved functional stability of a coarse-grained Ti-50.8 at.% Ni shape memory alloy achieved by precipitation on dislocation networks

Wang

Yang

et al. 2019

Scripta Materialia

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In this work, a new process is developed to improve the functional stability of Ni-rich NiTi alloys. Repetitive temperature-and stress-induced phase transformation is first conducted to generate dislocation networks in the grain interior. Dislocations serve as nucleation sites for Ni4Ti3 nanoprecipitates, which are formed after subsequent low-temperature (523 K) aging. With the presence of dislocations, a homogeneous distribution of nanoprecipitates in the grains is expected, enhancing the strength of the NiTi matrix and resisting plastic deformation during the martensitic transformation. As a result, an improved functional stability of NiTi alloys is achieved.

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Mechanisms for phase transformation induced slip in shape memory alloy micro-crystals

Cited by 79 publications

References 27 publications

B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

A microstructure-based constitutive model accounting for rate dependence of superelastic NiTi alloy under cyclic deformation

Improved functional stability of a coarse-grained Ti-50.8 at.% Ni shape memory alloy achieved by precipitation on dislocation networks

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Mechanisms for phase transformation induced slip in shape memory alloy micro-crystals

Cited by 79 publications

References 27 publications

B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

B2 ⇒ B19′ ⇒ B2T Martensitic Transformation as a Mechanism of Plastic Deformation of NiTi

A microstructure-based constitutive model accounting for rate dependence of superelastic NiTi alloy under cyclic deformation

Improved functional stability of a coarse-grained Ti-50.8 at.% Ni shape memory alloy achieved by precipitation on dislocation networks

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Improved functional stability of a coarse-grained Ti-50.8 at.% Ni shape memory alloy achieved by precipitation on dislocation networks