Thermomechanical cyclic response of an ultrafine-grained NiTi shape memory alloy

Kockar, Benat; Караман, И.; Kim, J.I.; Chumlyakov, Yuriy; Sharp, Jeff; Yu, C. J.

doi:10.1016/j.actamat.2008.04.001

Cited by 197 publications

(102 citation statements)

References 51 publications

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“…It is interesting to note that the linear fits in Figure 8 Kockar et al [29] explained this two-slope stress-transformation temperature relationship by a large elastic modulus mismatch between the transforming phases especially at close proximity to M r s due to lattice softening and by the inelastic accommodation of this mismatch. As the accommodation proceeds, the defect density is expected to increase, leading to a need for larger undercooling to grow martensite.…”

Section: Effect Of Sc Addition On Thermal Hysteresismentioning

confidence: 97%

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Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

Atli

Караман

Noebe

et al. 2010

Metall Mater Trans A

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A Ti 50.5 Ni 24.5 Pd 25 high-temperature shape memory alloy (HTSMA) is microalloyed with 0.5 at. pct scandium (Sc) to enhance its shape-memory characteristics, in particular, dimensional stability under repeated thermomechanical cycles. For both Ti 50.5 Ni 24.5 Pd 25 and the Sc-alloyed material, differential scanning calorimetry is conducted for multiple cycles to characterize cyclic stability of the transformation temperatures. The microstructure is evaluated using electron microscopy, X-ray diffractometry, and wavelength dispersive spectroscopy. Isobaric thermal cycling experiments are used to determine transformation temperatures, dimensional stability, and work output as a function of stress. The Sc-doped alloy displays more stable shape memory response with smaller irrecoverable strain and narrower thermal hysteresis than the baseline ternary alloy. This improvement in performance is attributed to the solid solution hardening effect of Sc.

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Section: Effect Of Sc Addition On Thermal Hysteresismentioning

confidence: 97%

“…To put these cyclic changes into perspective, equiatomic hot-rolled TiNi with a similar microstructure to these alloys, exhibits a shift of 9 K in M s temperature [29] after five thermal cycles.…”

Section: A Phase Transformation Temperaturesmentioning

confidence: 99%

Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

Atli

Караман

Noebe

et al. 2010

Metall Mater Trans A

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“…Reports are also available mentioning that B2 austenite phase is more stable against amorphization than B19 I martensite phase [26]. However, from the conventional load-elongation studies, it is known that when the austenite phase is deformed, after the initial elastic response, stressinduced martensite (SIM) transformation takes place followed by the elastic and plastic responses of SIM leading to failure [28,29]. Recently, similar to the present observation, Tyumentsev et al [30] observed deformation of B2 phase yielding B2 on rolling of NiTiFe single crystals.…”

Section: Effect Of Hpt Applied On the As-received Conditions Of Alloysmentioning

confidence: 98%

Stability of thermal-induced phase transformations in the severely deformed equiatomic Ni–Ti alloys

2012

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Nickel-Titanium (Ni-Ti) alloys of two different near-equiatomic chemical compositions (Ni-rich and Ti-rich) are subjected to severe plastic deformation by means of high pressure torsion (HPT) by higher rotation speed and larger total number of rotations. Further, the as-received and severely deformed specimens are subjected to heat treatments at 300 and 350°C. Phase transformations of the specimens under different conditions are analyzed by employing differential scanning calorimetry and by X-ray diffraction. The results obtained show that in Ti-rich Ni-Ti alloy the sequence of phase transformations is found to be stable against heat treatments and independent of previous HPT process. Also, in Ni-rich Ni-Ti alloy, when it is subjected to HPT, the sequence of phase transformations found to remain unaltered. However, with or without HPT, after the heat treatments at 300 and 350°C, the sequence of the phase transformation is found to be affected.

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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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Thermomechanical cyclic response of an ultrafine-grained NiTi shape memory alloy

Cited by 197 publications

References 51 publications

Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

Stability of thermal-induced phase transformations in the severely deformed equiatomic Ni–Ti alloys

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

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