Ordering kinetics in Cu-Al-Ni shape memory alloys

The atomic order has a strong influence on the martensitic transformation b ehavior in Cu-based shape memory alloys. In this work we have studied the i nfluence of the quenching and postquench aging treatments on the atomic ord er of the metastable beta phase obtained by quenching in Cu-Al-Ni shape mem ory alloys by means of thermoelectric power (TEP) measurements. The initial evolution of TEP during aging shows two clear stages where TEP value decre ases. These two TEP stages are interpreted as ordering processes at nearest neighbors (B2 order), and ordering processes at next nearest neighbors (L2 (1) order), respectively. The analysis of the isothermal kinetics during ag ing at different temperatures has allowed us to determine the activation en ergies for both ordering processes. (C) 1999 American Institute of Physics. [S0021-8979(99)01121-4].