MS-EVOLUTION IN CU-ZN-AL SMA - PREDICTABLE TEMPERATURE AND TIME ACTIONS ON PARENT PHASE

Recently an increased interest has been noticed for order effects in C u-based SMA. For instance, on the transformation temperature Ms values and its evolution after heat treatments and quench type effects, Usua lly, 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 res olution in temperature, time and resistance measurements on a Cu-Zn-Al alloy (1.48 e/a): the results establish a distribution of the evoluti on in two main actions: a relatively short time and a long time tail e ffects. Two temperature dependent time constants have been determined from the experiments, with different activation energies(13630 K and 1 0330 K). The two actions might be associated to different ordering pro cesses. Furthermore, the experimental results allow to describe a repr esentative model that can be used to predict the Ms evolution with tem perature and time. The differences between simulated and experimental results for the Ms is about +/- 0.15 K for temperature-time evolutions near room temperature.