Evolution of the shape memory parameters during multiple transformation cycles under load in Cu-Zn-Al alloys

The Cu-Zn-Al alloys with relatively small hysteresis(< 10 K) have been produced for the wire drawing and spring production for special applications. Response of the functional properties under various schemes of the transformation cycles is studied in detail in the final product form. Namely, the shift in the transformation temperatures and the features of the hysteresis loop observed in experiments with the stroke versus temperature dependence are analyzed as a function of the number of the full and partial transformation cycles. Degradation of the shape memory parameters with multiple transformation cycles occurs presumably in partial transformation cycles in the constrained condition. The behavior of the material in the transformation cycles under load is compared with the transformation cycles in the stress-free condition in order to propose finally the training scheme to reach optimal functional properties. (C) 1999 Elsevier Science S.A. All rights reserved.