Deformation mechanisms in a TiNi shape memory alloy during cyclic loading

Abstract

Deformation mechanisms governing the cyclic stress-strain behaviour of a TiNi shape memory alloy are investigated in this work. In order to understand the implementation of these mechanisms during cyclic loading, three low cycle fatigue tests were performed and stopped at different stages. The first test was stopped after the first cycle, the second one after 40 cycles corresponding to the beginning of the stabilization of the cyclic strain-stress behaviour and the last one was carried out up to failure (3324 cycles). Submitted to fatigue loading, the response of the TiNi shape memory alloy presents a classical pseudoelastic response. Two deformation mechanisms, identified by TEM observations, are highlighted, the first one by twins and the second by dislocation slip and their interaction with precipitates. These two mechanisms evolve without competition during cyclic loading. In the same time, nanomechanical properties were also examined and an evolution of the microhardness or indentation modulus has been noticed.

Fatigue and nanomechanical properties of K3XF nickel‐titanium instruments

“…Two mechanisms evolve without competition during cyclic loading: microtwinning and gliding dislocation (Gloanec et al . ). Both work hardening and work softening may be observed on the NiTi shape memory alloy during the cyclic fatigue process (Gloanec et al .…”

“…Both work hardening and work softening may be observed on the NiTi shape memory alloy during the cyclic fatigue process (Gloanec et al . ). In the present study, the nanohardness on cross sections of superelastic K3 NiTi instruments had slightly increased after‐fatigue tests.…”

“…The deformation mechanisms governing the cyclic stressstrain behaviour of a NiTi shape memory alloy are complicated. Two mechanisms evolve without competition during cyclic loading: microtwinning and gliding dislocation (Gloanec et al 2013). Both work hardening and work softening may be observed on the NiTi shape memory alloy during the cyclic fatigue process (Gloanec et al 2013).…”

“…Two mechanisms evolve without competition during cyclic loading: microtwinning and gliding dislocation (Gloanec et al 2013). Both work hardening and work softening may be observed on the NiTi shape memory alloy during the cyclic fatigue process (Gloanec et al 2013). In the present K3XF nanomechanical properties Shen et al study, the nanohardness on cross sections of superelastic K3 NiTi instruments had slightly increased after-fatigue tests.…”

Alloying effect on K shell X-ray fluorescence cross-sections and yields in Ti-Ni based shape memory alloys

“…Recently, shape memory alloys (SMAs) have attracted much interest as functional materials. Ti-Ni based SMAs are the most important technological alloys due to have unique special properties such as thermal shape memory effect, high damping capacity at room temperature, superelasticity, ductility, good mechanical strength, good fatigue strength, better corrosion resistance and low elastic modulus (Gloanec, Bilotta, & Gerland, 2013;Kang, Yoon, Kim, Nam, & Gjunter, 2002;Yadav, Rai, Subrahmanyam, & Srivastava, 2006). Due to the above mentioned unique features of Ti-Ni based SMAs, these alloys have been widely used in different technological applications such as sensors, actuators, medical devises, robots, separators, biomedical, automobile devices, guide wires for catheters (Aydo gmuş & Bor, 2011;Pıeczyska and Tobushı, 2011;Tobushi, Ikai, Yamada, Tanaka, & Lexcellent, 1996).…”