Heating rate effects on reverse martensitic transformation in a Cu – Zn – Al shape memory alloy

Abstract

Abstract Different fragments of martensitic Cu-14.86 Zn-5.81 Al-0.5 Fe (mass.%) shape memory alloy were subjected to heating, up to 453 K, with different rates ranging from 1.66 ×10−2 K s−1 to 54.6 × 1.66 × 10−2 K s−1, performed by means of a differential scanning calorimeter. In all cases, during heating, an endothermic peak was observed which was associated with the martensite reversion to parent phase. By means of the differential scanning calorimeter charts the critical transformation temperatures of martensite reversion were determined using the tangent method. The effects of heating rate were evaluated from the point of view: (i) of variation tendencies of critical transformation temperatures; (ii) of deviations of experimental values from linear fit and extrapolation to zero heating rate; and (iii) of corroborating morphological changes of martensite (sub)plates with heat flow variation particularities. The results prove that there is an obvious tendency of critical transformation temperatures, of reverse martensitic transformation, to linearly increase with heating rate. The effectiveness of the linear relationships was checked for two heating rate values located inside and outside the above mentioned range, respectively and the difference between the experimental and calculated values of critical transformation temperatures fell within the range (−3 … +4) ‰.