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

Nicoleta-Monica Lohan,Bogdan Pricop,Çtefan-Lucian Toma,Mihai Popa,Alin Marian Cazac,M Lazar,M Popescu-Stelea,F Faur

doi:10.1051/matecconf/202134206007

Nicoleta-Monica Lohan, Bogdan Pricop + Show 6 more

Open Access

https://doi.org/10.1051/matecconf/202134206007

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Abstract

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.

Highlights

Shape memory alloys (SMAs) are a group of materials that are part of the “smart materials” category
It can be noticed that the samples present a single stage transformation and the endothermic peak is attributed to the reverse martensitic transformation (MT) between monoclinic B19' type crystal structure and cubic B2 type crystal structure [24, 25, 26, 27]
Considering that the height of the peak is directly proportional to the transformation speed [28], in the case of NiTi alloy, the speed of the reverse MT is higher than that of direct transformation

Summary

Introduction

Shape memory alloys (SMAs) are a group of materials that are part of the “smart materials” category. The SMAs have various properties such as: ductility [1], strength [2], good biocompatibility [3], specific functional properties like shape memory effect [4], pseudeoelasticity [5] and superelasticity (SE) [6]. Due to these properties, they have a myriad of applications in many fields: biomedical [7], construction [8, 9], aerospace [10], automobile [11, 12], robotics [13], and even extraterrestrial roving missions [14]. In the case of medical applications, a high percentage of Ni can cause biocompatibility problems due to allergic, toxic and carcinogenic effect that Ni has [3] For these reasons, it is necessary to introduce a third alloying element in order to remove these limitations. The alloying of Ni-Ti with Nb leads to a higher thermal hysteresis, which is useful in the case of coupling elements used on an industrial scale [23]

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