Effect of ambient temperature on compressibility and recovery of NiTi shape memory alloys as static seals

The objective of this study was to investigate the effect of ambient temperature on compressibility and recovery of NiTi shape memory alloys as static seals. Experimental results indicated that compressibility and recovery of NiTi alloys were dependent on ambient temperature. At T < Af (the austenite finish temperature), the compressibility and recovery coefficients were almost unchanged when the compression stress was higher than a certain level. The residual strain of NiTi alloys increased with a decrease in temperature at T < Af. The residual strain of NiTi alloys was remarkably high at the temperature below Mf (the martensite finish temperature). The recovery coefficient of NiTi alloys at T > Af gradually increased with increasing compression loading. The compressibility and recovery coefficients of NiTi alloys were insignificantly fluctuated at the temperatures between 60°C and 150°C upon the compression loading. The features of strong deformation and martensite reorientation in the compressed NiTi alloys confirmed the temperature effect.

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On the partial recovery of residual strain accumulated during an interrupted cyclic loading of NiTi shape memory alloys

Smart Materials and Structures ◽

10.1088/0964-1726/17/6/065027 ◽

2008 ◽

Vol 17 (6) ◽

pp. 065027 ◽

Cited By ~ 5

Author(s):

A Paradis ◽

P Terriault ◽

V Brailovski ◽

V Torra

Keyword(s):

Cyclic Loading ◽

Shape Memory Alloys ◽

Shape Memory ◽

Residual Strain ◽

Partial Recovery ◽

Niti Shape Memory Alloys

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Multi-stage martensitic transformation in Ni-rich NiTi shape memory alloys

Functional Materials Letters ◽

10.1142/s1793604717400045 ◽

2017 ◽

Vol 10 (01) ◽

pp. 1740004 ◽

Cited By ~ 15

Author(s):

Xiebin Wang ◽

Bert Verlinden ◽

Sergey Kustov

Keyword(s):

Martensitic Transformation ◽

Shape Memory Alloys ◽

Shape Memory ◽

Precipitation Hardening ◽

Aging Treatment ◽

Functional Stability ◽

Transformation Behavior ◽

Niti Alloys ◽

Multi Stage ◽

Niti Shape Memory Alloys

Precipitation hardening is an effective way to improve the functional stability of NiTi shape memory alloys. The precipitates, mainly Ni4Ti3, could be introduced by aging treatment in Ni-rich NiTi alloys. However, the presence of Ni4Ti3 precipitates could disturb the transformation behavior, resulting in the multi-stage martensitic transformation (MMT). With the presence of MMT, it is difficult to control the transformation behavior, and thus limits the applicability of NiTi alloys. In this work, previous efforts on explaining the observed MMT are summarized. The difficulties in developing a unified explanation are discussed, and a possible way to avoid the MMT is proposed.

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Influence of alloying elements on the thermal behavior of NiTi shape memory alloys

MATEC Web of Conferences ◽

10.1051/matecconf/202134206007 ◽

2021 ◽

Vol 342 ◽

pp. 06007

Author(s):

Nicoleta-Monica Lohan ◽

Çtefan-Lucian Toma ◽

Mihai Popa ◽

Alin Marian Cazac ◽

Bogdan Pricop

Keyword(s):

Shape Memory Alloys ◽

Thermal Behavior ◽

Shape Memory ◽

Alloying Elements ◽

Alloying Element ◽

Scanning Calorimetry ◽

Automotive Manufacturing ◽

Niti Alloys ◽

The Third ◽

Niti Shape Memory Alloys

NiTi based shape memory alloys are one of the most intensely studied alloys from its class. Therefore, diverse commercial applications have been developed due to certain properties such as: shape memory effect, superelasticity and corrosion resistance. Currently, the main applications of NiTi alloys are automotive manufacturing and aerospace actuators, biomedical devices or pipe couplings. In recent years, NiTi shape memory alloys have been alloyed with a third element in order to improve the above-mentioned properties. In order to investigate the influence of the alloying elements on the thermal behavior of NiTi alloys, the addition of the third alloying element (Ta and Nb) is under investigation in the present study. The thermal behavior of the three alloys (NiTi, NiTiNb and NiTiTa) was studied by differential scanning calorimetry. Following the experiments, it was observed that the addition of the third alloying element influences the critical transformation temperatures.

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