Micromechanical quantification of elastic, twinning, and slip strain partitioning exhibited by polycrystalline, monoclinic nickel–titanium during large uniaxial deformations measured via in-situ neutron diffraction

Stebner, Aaron P.; Vogel, Sven C.; Noebe, Ronald D.; Sisneros, Thomas A.; Clausen, B.; Brown, Donald W.; Garg, A.; Brinson, L. Catherine

doi:10.1016/j.jmps.2013.05.008

Cited by 112 publications

(71 citation statements)

References 69 publications

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“…This finding, together with the nearly full recovery of strain while holding at 0 load, indicate that in this condition the resistance of the material to passing transformation fronts is small. In fact, the microstructure appears to be assisting transformation at a rate that is much slower than the bulk deformation strain rate of 5 9 10 -4 , and also much slower than would be expected of a simple slip or twinning-related Bauschinger effect, such as those previously observed in monoclinic NiTi [34] as well as B2 and mixtures of B2 ? B19' NiTi [35] at analogous unloading rates.…”

Section: Effects Of Tensile Pre-strain Between 8 and 10 %mentioning

confidence: 81%

“…It could be due to (1) deformation twinning or (2) merely due to more of the martensite formed of {110} A grains being retained, while more of the martensite of {211} A grains transformed back during unloading. However, these orientations are not related by {112} A , [24] and e_(hkl) were used to calculate changes of the residual stress component in the load direction for each of the reflections {113} A , or {114} A compound twinning, the most favorable and previously observed B2 twin systems for Nitinol [34,[38][39][40]. Therefore, these observations are probably due to the transformation mechanism.…”

Section: Effects Of Tensile Pre-strain Between 8 and 10 %mentioning

confidence: 99%

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In Situ Neutron Diffraction Studies of Increasing Tension Strains of Superelastic Nitinol

Pelton¹,

Clausen

Stebner

2015

Shap. Mem. Superelasticity

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A micromechanical study of the effect of varying amounts of tensile strains on the microstructures and subsequent mechanical behaviors of superelastic Nitinol rods is presented. It is found that strains up to *8-9 % develop microstructures that assist both forward and reverse transformation relative to un-strained material. This superelastic phenomenon is explained to be analogous to two-way shape memory effect in Nitinol actuation materials. These results provide understanding as to why such ''pre-strains'' may lead to improvements in subsequent superelastic fatigue life. Beyond 9 %, a drastic change is observed, as large amounts of martensite (75 % and more) are retained in unloaded samples. Thus, a competition between transformation, plasticity, and reorientation is found to give rise to microstructures that inhibit complete transformation. Furthermore, even though similar inelastic strain magnitudes are observed in loading and unloading plateaus, micromechanical mechanisms differ substantially from samples with less pre-strain. For example, in highly pre-strained samples at least half of the plateau strains are due to martensite reorientation, whereas, in low and moderately pre-strained samples nearly the entirety of the plateau strain is due to transformation. We also find that latent heat of plastic flow is larger than latent heat of transformation.

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Section: Effects Of Tensile Pre-strain Between 8 and 10 %mentioning

confidence: 81%

Section: Effects Of Tensile Pre-strain Between 8 and 10 %mentioning

confidence: 99%

In Situ Neutron Diffraction Studies of Increasing Tension Strains of Superelastic Nitinol

Pelton¹,

Clausen

Stebner

2015

Shap. Mem. Superelasticity

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“…4b and d) and no plastic strain was observed during the initial loading to 1 GPa. The strong tension-compression asymmetry is due to differences in martensitic variant selection (variant reorientation and detwinning) in tension and compression deformation modes as was observed in binary NiTi alloy [22,23]. This deformation strain, 3.7% in tension and 2.2% in compression at 1 GPa stress, is a combination of elastic strain and inelastic martensite variant reorientation/detwinning, but no discernible stress plateau or demarcation between the two mechanisms was observed.…”

Section: Isothermal Behavior E Tension and Compressionmentioning

confidence: 84%

Mechanical and functional behavior of a Ni-rich Ni50.3Ti29.7Hf20 high temperature shape memory alloy

et al. 2014

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a b s t r a c tThe mechanical and functional behaviors of a Ni-rich Ni 50.3 Ti 29.7 Hf 20 high temperature shape memory alloy were investigated through combined ex situ macroscopic experiments and in situ synchrotron X-ray diffraction. Isothermal tension and compression tests were conducted between room temperature and 260 C, while isobaric thermomechanical cycling experiments were conducted at selected stresses up to 700 MPa. Isothermal testing of the martensite phase revealed no plastic strain up to the test limit of 1 GPa and near-perfect superelastic behavior up to 3% applied strain at temperatures above the austenite finish. Excellent dimensional stability with greater than 2.5% actuation strain without accumulation of noticeable residual strains (at stresses less than or equal to À400 MPa) were observed during isobaric thermal cycling experiments. The absence of residual strain accumulation during thermomechanical cycling was confirmed by the lattice strains, determined from X-ray spectra. Even in the untrained condition, the material exhibited little or no history or path dependence in behavior, consistent with measurements of the bulk texture after thermomechanical cycling using synchrotron X-ray diffraction. Post deformation cycling revealed the limited conditions under which a slight two-way shape memory effect (TWSME) was obtained, with a maximum of 0.34% two-way shape memory strain after thermomechanical cycling under À700 MPa.Published by Elsevier Ltd.

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“…Some key performance issues include the potential for structural fatigue, whereby cracks may nucleate and lead to component failure [52] and also functional fatigue, whereby cyclic strain may accumulate under a sustained macroscopic stress from a variety of mechanisms in the martensite phase [53] as well as plasticity in the austenite phase [54][55][56][57], particularly at elevated temperature [58]. For Al matrix composites, such cyclic straining can arise from a mismatch in coefficients of thermal expansion, even in the absence of any phase transformations [59].…”

Section: Discussionmentioning

confidence: 99%

Deformation Mechanisms in NiTi-Al Composites Fabricated by Ultrasonic Additive Manufacturing

Chen

Hehr

Dapino

et al. 2015

Shap. Mem. Superelasticity

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Thermally active NiTi shape memory alloy (SMA) fibers can be used to tune or tailor the effective coefficient of thermal expansion (CTE) of a metallic matrix composite. In this paper, a novel NiTi-Al composite is fabricated using ultrasonic additive manufacturing (UAM). A combined experimental-simulation approach is used to develop and validate a microstructurally based finite element model of the composite. The simulations are able to closely reproduce the macroscopic strain versus temperature cyclic response, including initial transient effects in the first cycle. They also show that the composite CTE is minimized if the austenite texture in the SMA wires is h001i B2 , that a fiber aspect ratio [10 maximizes fiber efficiency, and that the UAM process may reduce hysteresis in embedded SMA wires.Keywords SMA Á Composite material Á Coefficient of thermal expansion Á Finite element analysis Á Ultrasonic additive manufacturing Á Thermomechanical behavior

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Micromechanical quantification of elastic, twinning, and slip strain partitioning exhibited by polycrystalline, monoclinic nickel–titanium during large uniaxial deformations measured via in-situ neutron diffraction

Cited by 112 publications

References 69 publications

In Situ Neutron Diffraction Studies of Increasing Tension Strains of Superelastic Nitinol

In Situ Neutron Diffraction Studies of Increasing Tension Strains of Superelastic Nitinol

Mechanical and functional behavior of a Ni-rich Ni50.3Ti29.7Hf20 high temperature shape memory alloy

Deformation Mechanisms in NiTi-Al Composites Fabricated by Ultrasonic Additive Manufacturing

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