Abstract
Reliability is a critical word in industrial applications of Shape Memory Alloys (SMA) usually called smart materials. Applications of these materials require a rigorous stability of the transformation temperatures and a small hysteresis. The applications of the SMA to the continuous actuators involve a time guarantee about the constructed devices related to the suitable composition and heat treatment. From a mechanical model for a single martensite plate, the shape of the hysteresis cycle (single crsytal of Cu-Zn-Al alloys) is obtained by generalizing the representation to N plates. The observed time effects on the hysteresis loops related to diffusion processes were also taken into account. They allow to explain the martensite recoverable creep and the micromemory effects. Using high resolution on resistance measurements, the room temperature effects on the parent phase acting over the transformation temperature Ms is evaluated. The effect produced by two atomic order parameters (i. e. B2 and L21) related to the yearly room temperature evolution (for instance, summer to winter) induces predictive evolution of transformation temperature and the mean uncertainty reduces drastically (δMs≈±0.05).
