Superelasticity and Shape Memory Effect in Cu-Sn Alloys

Abstract

The martensitic transformation and the mechanical behavior in β-Cu-Sn alloy,mainly the composition of Cu-15.0 and 15.3 at.%Sn, have been studied by means of electrical resistivity measurements, X-ray diffraction patterns and tensile tests. The martensitic transformation temperature in Cu-Sn alloys decreased with increasing tin contents and the crystal structures of both thermal and stress-induced martensites in Cu-15.3 at.%Sn were found to be orthorhombic. The shape memory effect of thermal martensite in Cu-15.0at.%Sn alloy appears only for a slightly deformation, and the effect is mostly concerned with the stress-induced martensite in Cu-Sn alloy. After ageing at room temperature in β 1 phase, the tensile behavior showed remarkable superelasticity and critical stress to induce the martensite increased with increasing ageing time and deformation temperature. And also,the strain rate dependence of superelastic behavior was remarkable, at the lower strain rate the superelasticity disappeared because of the stabilization of the stress-induced marten-site.