Two way shape memory effect in Cu-Al-Ni single crystals

The two way shape memory effect (TWSME) was induced in Cu-Al-Ni single crys tals by a training method which consisted of applying tensile or compressiv e stresses at room temperature and keeping the sample under stress in the m artensitic phase at the same temperature for a certain time. After quenchin g from the beta stability region the studied alloys exhibit a simultaneous transformation to beta'(18R) and gamma' (2H) martensites. Subsequent ageing in the beta phase favours the formation of the gamma' phase. An important improvement of the TWSME has been obtained both in the tension and compress ion modes in the samples aged at 470 K before training, coincident with a t ransformation predominantly to the gamma' martensitic phase. In trained sam ples, a subsequent heating for short times at 520 K produces a stable and m aximum TWSME of 4% always in elongation sense, both for the samples trained in tension and compression mode. (C) 1999 Elsevier Science S.A. All rights reserved.