Pseudoelasticity in Au-Cd thermoelastic martensite

Abstract

Thermoelastic martensitic transformation has been studied by the analysis of stress-strain curves in binary Au-Cd alloys, containing 46·5, 47·5, 48·5, 49, 49·5, and 50 at. % Cd, respectively. The pseudoelastic characteristics, i.e. superelastic and ferroelastic behaviour upon tension compression test and that the origin of the shape memory effect bears a close relation to the ferroelastic loop, have been explained on the basis of the lattice softening, that is. the shear elastic constant, C′ = (C₁₁-C₁₂)/2, decreases toward zero in the vicinity of the transition temperature. In particular the critical condition for obtaining the ferroelastic loop can be experimentally determined by assuming a critical stress, which is termed ‘ferroelastic limit’. The ferroelastic limit may depend upon the elastic anisotropy of alloys and lies in the region 6 Kg/mm- in the Au-Cd alloy.