Microstructure, superelasticity and shape memory effect by stress-induced martensite stabilization in Cu–Al–Mn–Ti shape memory alloys

In this study, the microstructure, martensitic transformation, superelasticity, stabilization of stress-induce martensite and the corresponding shape memory effect of Ti-doped Cu–Al–Mn shape memory alloys were investigated. The results show that the present Cu–Al–Mn–Ti alloys consist of two types of L2₁ phases, including Cu₂AlMn parent and Cu₂TiAl precipitate. The dispersive L2₁–Cu₂TiAl precipitates strengthen the stabilization of stress-induced 2H(γ′₁) martensite from L2₁–Cu₂AlMn parent. Thus, all studied alloys show not only superelasticity at deformation, but also shape memory effect after unloading by heating. Consequently, the Cu–12.9Al–8.3Mn–0.5Ti alloy (wt%) possesses the best superelastic strain up to 4.6% and a shape memory effect of 1.5% under a pre-deformation of 11%, while Cu–12.8Al–7.7Mn–2.6Ti alloy (wt%) shows the best shape memory effect up to 2.5% simultaneously showing 1.9% of superelastic strain with a pre-deformation of 10%.