Thermodynamic study of the temperature memory effects in Cu–Al–Ni shape memory alloys

Abstract

This work presents careful adiabatic calorimetry measurements of the temperature memory effects on a Cu–Al–Ni shape memory alloy single crystal. These effects, which appear after partial martensitic transformations, have been systematically studied. The subsequent delay of the transformation as a function of the thermal history is described by means of a straightforward model, which makes full use of the phase transformation thermodynamic functions, carefully determined from the specific heat results. This model predicts on quantitative grounds, the decrease in the transformed mass in the successive thermal cycles. It also provides information about the distribution of the elastic energy among the martensitic plates in the low temperature phase, which is a characteristic feature of these alloys. The knowledge of the elastic states is not only required to analyze the properties of the martensitic phase but also to describe the kinetics of any physical quantity in the reverse transformation.