Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

Benafan, Othmane; Noebe, Ronald D.; Padula, Santo; Vaidyanathan, R.

doi:10.1007/s11661-012-1297-z

Cited by 86 publications

(39 citation statements)

References 52 publications

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“…Solutionized samples were then sectioned into 7 × 7 × 1 mm 3 slices, so that aging at 550, 600 and 800 • C for various times could be examined under the same starting metallurgical conditions. Aging at 550 • C was chosen since it is the generally accepted peak aging temperature for Ni-rich NiTiHf/Zr HTSMA [7,18,26]. Aging at 600 • C was chosen since this will increase the precipitation rate.…”

Section: Methodsmentioning

confidence: 99%

“…In Figure 5c, the Ni-rich 1-D diffraction data, a different broad peak is observed, centered at 2.21 Å, in the diffraction data when the alloy is treated at 550 °C or 600 °C. This peak has been indexed as the nano-strengthening Hphase seen in other NiTiZr and NiTiHf HTSMAs compositions [7,17,18,23,26,28] using the basis positions from Yang et al [24]. Once the temperature increases to 800 °C, the presence of the broad H-phase peak is no longer observed, but rather the sharp residual austenite peak at 2.19 Å is observed instead.…”

Section: Microstructural and High Energy Synchrotron Radiation X-ray mentioning

confidence: 99%

“…Through this research, Ni-Ti-based shape memory alloys (SMAs) have now become an important technological material for a wide array of applications [3,4], i.e., specifically medical devices [5], actuators [6], etc. Despite this eclectic and ever-expanding list of applications, there exists more opportunity to enlarge the realm of potential uses by increasing the temperatures at which the characteristic phase transformation occurs, most notably in the aerospace industry [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

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Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

Carl

Smith

Doren³

et al. 2017

Metals

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Abstract:The effect of Ni-content on phase transformation behavior of NiTi-20 at. % Zr high temperature shape memory alloy (HTSMA) is investigated over a small composition range, i.e., 49.8, 50.0 and 50.2 at. % Ni, by differential scanning calorimetry (DSC), high-energy synchrotron radiation X-ray diffraction (SR-XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). All samples show a monoclinic B19 martensitic structure at room temperature. It is shown that even with these small variations in Ni-content, the alloy shows vastly different transformation temperatures and responds in a drastically different manner to aging treatments at 550 and 600 • C. Lastly, a discussion on H-phase composition with respect to bulk composition is presented.

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Section: Methodsmentioning

confidence: 99%

Section: Microstructural and High Energy Synchrotron Radiation X-ray mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

Carl

Smith

Doren³

et al. 2017

Metals

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“…However, certain thermal treatments of Ni-rich Ni-TiHf/Zr HTSMAs have been recently revealed as an effective method to improve the shape memory response of these alloys [28][29][30][31][32][33][34][35][36][37] and to overcome the limitations of the (Ti ? Hf/Zr)-rich compositions.…”

Section: Ni-ti-hf/zr Alloysmentioning

confidence: 99%

Effect of Thermal Treatments on Ni–Mn–Ga and Ni-Rich Ni–Ti–Hf/Zr High-Temperature Shape Memory Alloys

Santamarta

Evirgen

Pérez-Sierra

et al. 2015

Shap. Mem. Superelasticity

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Among all the promising high-temperature shape memory alloys (HTSMAs), the Ni-Mn-Ga and the Ni-Ti-Hf/Zr systems exhibit interesting shape memory and superelastic properties that may place them in a good position for potential applications. The present work shows that thermal treatments play a crucial role in controlling the martensitic phase transformation characteristics of both systems, but in different ways. On one hand, the equilibrium phase diagram of the Ni-Mn-Ga family allows selecting compositions with high transformation temperatures and outstanding thermal stability at relatively high temperatures in air, showing no significant changes in the transformation behavior for continuous aging up to *5 years at 500°C. Moreover, the excellent thermal stability correlates with a good thermal cyclic stability and an exceptional oxidation resistance of the parent phase. On the other hand, precipitation processes controlled by thermal treatments are needed to manipulate the transformation temperatures, mechanical properties, and thermal stability of Ni-rich Ni-Ti-Hf/Zr alloys to become HTSMAs. These changes in the functional properties are a consequence of the competition between the mechanical and compositional effects of the precipitates on the martensitic transformation.

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“…This material has been shown to exhibit outstanding strength and stability during constantstress, thermal cycling experiments (i.e., actuation) [24][25][26][27], at least for a limited number of cycles. On the other hand, constant-strain thermal cycling experiments to determine the recovery stress of this specific alloy have not been previously reported.…”

Section: Introductionmentioning

confidence: 99%

Constant-Strain Thermal Cycling of a Ni50.3Ti29.7Hf20 High-Temperature Shape Memory Alloy

Benafan

Noebe

Halsmer

et al. 2016

Shap. Mem. Superelasticity

Self Cite

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The effect of various pre-straining routines on the recovery stresses of a Ni-rich Ni 50.3 Ti 29.7 Hf 20 hightemperature shape memory alloy was investigated in tension and compression. The recovery stresses, obtained by means of constant-strain thermal cycling, were evaluated after isothermal (up to ±2 % applied strain at room temperature) or after isobaric thermal cycling at stress levels between ±100 and 400 MPa. The material exhibited high force generation capability with recovery stresses of nearly 1.5 GPa on the first cycle under particular pre-strain conditions. The recovery stresses are shown to decay during subsequent cycles using an upper cycle temperature of 300°C with a saturated stress level nearing 1.1 GPa in compression.

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Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

Cited by 86 publications

References 52 publications

Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

Effect of Ni-Content on the Transformation Temperatures in NiTi-20 at. % Zr High Temperature Shape Memory Alloys

Effect of Thermal Treatments on Ni–Mn–Ga and Ni-Rich Ni–Ti–Hf/Zr High-Temperature Shape Memory Alloys

Constant-Strain Thermal Cycling of a Ni50.3Ti29.7Hf20 High-Temperature Shape Memory Alloy

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