Influence of high temperature ternary and quaternary additions on the phase transformation and actuation fatigue characteristics of NiTi shape memory alloys

Shape memory alloys (SMAs) are a type of metal with two distinct properties: superelasticity and shape memory. When SMAs are subjected to thermomechanical treatment, they become responsive to stimuli such as thermal gradient. As a result, these alloys have shown to be useful in a variety of applications, including sensors and actuators, as well as different medical devices. When it comes to shape memory materials, Ni-Ti alloys are famous and have been used in a variety of applications. The demand for shape memory alloys with high transformation temperatures (HTSMA) has risen, owing not just to academic interest but also to market demand, particularly from the transportation and oil industries, as well as robots. The actuation fatigue performance of ternary HTSMA-Ni50Ti30Zr20/Hf-20 (at %) and quaternary HTSMA-Ni50Ti30Zr10Hf10 was evaluated and compared. Actuation fatigue tests were performed on both ternary and quaternary HTSMA on application of constant loads ranging from 250 to 450 MPa until failure occurred. This work concentrates on studying and comparing the temperatures at which phase transformation occurs before and after actuation fatigue tests were conducted, and to correlate the results for future development of HTSMAs.