The two-way memory effect by the pre-strain training method in a 50Ti40Ni10Cu (at.%) alloy

Abstract

The two-way memory effect (TWME) can be settled after a training of the shape memory alloy apt to stabilize the preferential growth (shrinkage) of martensite domains by decreasing (increasing) temperature. That appears as a consequence of a pattern of line defects which act as nucleation sites of selected variants growth. Though several training procedures have been suggested, a clear cut view of the most efficient one has not yet been reached. Recently a pre-strain method has been adopted to settle the TWME in TiNi alloys, with the highest reversible strain obtained for a plastic pre-strain introduced at temperatures (T) M{sub s}TA{sub f}. The TWME on 50Ti40Ni10Cu (at%) alloy has already been investigated with a training procedure based on a sequence of thermal cycles under applied stress involving the B2(parent) {leftrightarrow} B19(orthorhombic) transformation. Interest is here given to the pre-strain training TWME in a 50Ti40Ni10Cu (at%) alloy introducing the plastic prestrain either in monoclinic (B19{prime}), or in orthorhombic (B19), or in parent (B2) phase in the range of stress induced martensite.