Shape memory effect and superelasticity in high-strength FeNiCoAlTiNb single crystals

The effect of two-stage ageing in a stress-free state and under tensile stress on the precipitation processes of dispersed particles, temperature range of γ–α′ martensitic transformations (MT), superelasticity and shape memory effect was investigated on [001]-oriented single crystals of the Fe–28% Ni–17% Co–11.5% Al–2.5% TiNb (at %) alloy. It was shown that two-stage ageing leads to simultaneous precipitation of γ′- and β-phase particles. β-phase particles were not found to inhibit the γ–α′ MT and led to the appearance of a tensile two-way shape memory effect (TWSME), which was 3.8% in stress-assisted aged crystals. The reasons for the appearance of a TWSME were discussed.