Ligas com memória de forma : nitinol e suas aplicações

Abstract

This study aimed to conduct an in-depth investigation on Shape Memory Alloys (SMAs), with a particular focus on NiTi alloys due to their widespread usage, while also providing a brief historical background. The present work presents the main properties of SMAs, including their crystal structure, transformation mechanisms and temperatures, and the influence of alloying elements such as nickel proportion in Ni-Ti alloys, as well as the addition of aluminum and nickel in copper alloys. The impact of these elements on the thermal and mechanical properties is demonstrated. Through this initial theoretical foundation, a comprehensive understanding of the shape memory effect, which enables SMAs to recover their original shape upon heating, and superelasticity, which allows for reversible deformation without the need for heating, was achieved. Additionally, some examples of commercially significant alloys were presented, highlighting their key characteristics, such as the excellent corrosion resistance of NiTi alloys and the cost-effectiveness of copper alloys. The unique characteristics of SMAs, such as their remarkable regenerative capacity and their ability to function as both sensors and actuators simultaneously, owing to their distinctive phase transformations, make them essential for applications in medicine, aerospace industry, and electrical devices.