Ms-Evolution in Cu-Zn-Al SMA. Predictable Temperature and Time Actions on Parent Phase

Abstract
Recently an increased interest has been noticed for order effects in Cu-based SMA. For instance, on the transformation temperature Ms values and its evolution after heat treatments and quench type effects. Usually, the experimental Ms values after quench fluctuate around ± 2 K. The interest for continuous actuators needs a more reduced and, in any case, predictable fluctuation domain. In this work, by using high resolution in temperature, time and resistance measurements on a Cu-Zn-Al alloy (1.48 e/a), the results establish a distribution of the evolution in two main actions : a relatively short time and a long time tail effects. Two temperature dependent time constants have been determined from the experiments, with different activation energies (13630 K and 10330 K). The two actions might be associated to different ordering processes. Furthermore, the experimental results allow to describe a representative model that can be used to predict the Ms evolution with temperature and time. The differences between simulated and experimental results for the Ms is about ± 0.15 K for temperature-time evolutions near room temperature.