Lifetime of superelastic Cu–Al–Be single crystal wires under bending fatigue

Many applications of shape memory alloys require cyclic deformation, making fatigue behavior of material an important consideration in component design. Cu–Al–Be alloys are thermically very stable and show a high superelasticity especially in single crystalline form. In order to study fatigue lifetime of these alloys, tests were performed on Cu–Al–Be single crystal wires using a bending apparatus with imposed strain. For large deformation (10%), Cu–Al–Be single crystals have shown good fatigue properties, comparable to Ni–Ti at a deformation of 3%. As cycling proceeded, superficial striations patterns appeared, which were linked with the imposed strain. In surface striations, microcracks were observed which are assumed to cause the failure.