Session: 02-10: Design, Modeling, and Behavior of Functional and Shape Memory Materials and Composites

Paper Number: 112318

112318 - The Influence of Substitutional Elements in Hysteresis Reduction and Thermo-Mechanical Stability of Shape Memory Alloys 

Shape memory alloys (SMAs) have gained much attention as a powerful source of actuation due to their improved performance, reduced size, complexity between components, and high work output density. Their primary mechanism of actuation relies on a non-diffusional cyclic phase transformation from martensite to austenite, where the amount of thermal energy needed per cycle is directly associated with the hysteresis width between the austenite final and martensite final temperatures. Consequently, a narrower gap between those two temperature ranges requires a much lower energy demand to produce the actuation needed. Previous studies have indicated that the hysteresis width is linked to a strong coherence between the austenite/martensite interface. It has been shown that elemental additions to NiTi-based SMAs can further improve this coherency. Another huge challenge facing this unique technology is linked to its thermo-mechanical stability. Binary NiTi SMAs often exhibit significant transformation temperature shifts after each thermo-mechanical cycle, which requires a long training process and consequently contributes to higher production costs. The primary goal of this project is to understand the influence of substitutional elements as a precursor to hysteresis reduction and identify a thermo-mechanically stable low hysteresis shape memory alloy for actuator applications. To accomplish this goal, elemental additions of Cu and Pd were incorporated into NiTi-based SMAs. The results were compared with respect to their hysteresis width and thermo-mechanical stability through differential scanning calorimetry, scanning electron microscopy with energy dispersive spectroscopy, and compressive thermo-mechanical testing. Two quaternary SMAs containing small additions of Cu and Pd exhibited promising results concerning hysteresis width and excellent thermo-mechanical stability.

Presenting Author: Andre Montagnoli University of North Texas

Presenting Author Biography: Andre Montagnoli has been a student at the University of North Texas for the last 5 years, where he obtained both his BS and MS in Materials Science and Engineering. He is pursuing his doctorate in the same field, focusing on the effects of low hysteresis shape memory alloys for satellite actuators and the elasto-caloric effects of SMAs in mechanical refrigeration. After completing his Doctorate degree, Andre plans to continue working in the field of shape memory alloys and seek a career in aerospace engineering.