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 crystals by a training method which consisted of applying tensile or compressive stresses at room temperature and keeping the sample under stress in the martensitic phase at the same temperature for a certain time. After quenching from the β stability region the studied alloys exhibit a simultaneous transformation to β′(18R) and γ′ (2H) martensites. Subsequent ageing in the β phase favours the formation of the γ′ phase. An important improvement of the TWSME has been obtained both in the tension and compression modes in the samples aged at 470 K before training, coincident with a transformation predominantly to the γ′ martensitic phase. In trained samples, a subsequent heating for short times at 520 K produces a stable and maximum TWSME of 4% always in elongation sense, both for the samples trained in tension and compression mode.