Environment-Induced Degradation of Shape Memory Alloys: Role of Alloying and Nature of Environment

Abstract

Shape memory effects coupled with superelasticity are the distinctive characteristics of shape memory alloys (SMAs), a type of metal. When these alloys are subject to thermomechanical processing, they have the inherent ability to react to stimuli, such as heat. As a result, these alloys have established their usefulness in a variety of fields and have in recent years been chosen for use in stents, sensors, actuators, and several other forms of life-saving medical equipment. When it comes to the shape memory materials, nickel–titanium (Ni-Ti) alloys are in the forefront and have been chosen for use in a spectrum of demanding applications. As shape memory alloys (SMAs) are chosen for use in critical environments, such as blood streams (arteries and veins), orthodontic applications, orthopedic implants, and high temperature surroundings, such as actuators in aircraft engines, the phenomenon of environment-induced degradation is of both interest and concern. Hence, the environment-induced degradation behavior of the shape memory alloys (SMAs) needs to be studied to find viable ways to improve their resistance to an aggressive environment. The degradation that occurs upon exposure to an aggressive environment is often referred to as corrosion. Environment-induced degradation, or corrosion, being an unavoidable factor, certain techniques can be used for the purpose of enhancing the degradation resistance of shape memory alloys (SMAs). In this paper, we present and discuss the specific role of microstructure and contribution of environment to the degradation behavior of shape memory alloys (SMAs) while concurrently providing methods to resist both the development and growth of the degradation caused by the environment.

Snake Robot with Motion Based on Shape Memory Alloy Spring-Shaped Actuators

“…The selection of the shape depends on the application of the actuator; however, this poses limitations, as the programming process must be performed previously. One of the drawbacks of this kind of actuator is the degradation from the shape of the SMA due to the effect of constant loads that are applied over cyclical tasks, thus implying that the proposed structure must provide a physical structure that allows for substitution of the actuators once they surpass their number of duty cycles [ 52 , 53 ]. Of the various shapes that could be implemented using SMA actuators, one of the most used is the spring shape.…”