Superelasticity and shape memory effect in Cu–Al–Mn–V shape memory alloys

In this study, Cu–Al–Mn–V alloys with bcc phase separation were designed through changing V and Mn contents, resulting in complex microstructure consisted of L21 parent, small amounts of δ(V, Mn) and 2H(γ'1) martensite. The amounts of δ(V, Mn) phase and 2H(γ'1) martensite increase with the increase of V content. The results further show that the stabilization of stress-induced 2H(γ'1) martensite from L21 parent occurs among all Cu–Al–Mn–V alloys during deformation. Thus the same alloy not only exhibits superelasticity, but also shape memory effect after unloading when heated. The superelasticity and shape memory effect are summarized to three situations. Situation I includes Cu63.7Al25.3V1.9Mn9.1 and Cu63.7Al25.8V2.2Mn8.3 alloys (at.%), which have excellent superelasticity strains being up to 5.4% and 3.9% respectively. Cu63.8Al25.4V4.2Mn6.6 and Cu63.0Al26.2V4.7Mn6.1 alloys are situation II, and exhibit good shape memory effects being up to 3.5% and 3.9% respectively. The superelasticity and shape memory effect of Cu62.8Al26.2V2.6Mn8.4 alloy that is situation III are between the above two situations. The obtained results may open an avenue to design copper-based shape memory alloys simultaneously have superelasticity and shape memory effect under the same composition and deformation temperature through applying stress.