Production and Functionalization of Shape Memory Alloys for Actuator ApplicationsThursday (24.09.2020) 09:30 - 10:00 Z: Special Symposia II Part of:
Driven by the needs of industry for down-scaling, lightweight, noise-less and high work output actuation, NiTi-based shape memory alloys (SMAS) nowadays have found their role in several applications, among others they are used in automotive, aerospace, civil-engineering, consumer electronics, medical instruments, optical image stabilization, fasteners, heat conversion, thermal valves, heat sensors, robotics and many more. Even though several shape memory alloy systems were discovered in the last decades, binary and alloyed NiTi, which is then drawn by conventional methods into simple shapes like wires or springs, occupies still the largest market share. In order to exploit efficiently their extraordinary recovery properties of these shape memory alloys, effort needs to be taken from the preparation, processing and functionalization to the conversion into a finished product, because all the material history contributes to the final transformation characteristics.
This presentation sheds light on the fundamentals in NiTi melting and wire drawing which need to be performed with care for obtaining a homogenous, controlled chemistry with low amount of inclusions. In a following step, it will be discussed on how final transformation properties can be induced by an annealing and training process to award the alloys a favorable microstructure for actuator applications. Especially this last step is decisive as it allows for engineering key parameters like transformation temperatures, hysteresis width, shape recovery or recovery stress. In the end, a few examples are provided which illustrate the opportunities offered by shape memory alloys.