Calorimetry in Cu–Zn–Al alloys under different structural and microstructural conditions

Calorimetric measurements have been carefully performed on four kinds of Cu–Zn–Al samples, arising from the combination of different martensitic structures and from the presence or not of grain boundaries. The differences found in the transformation behaviour, characteristic transformation temperatures and in the corresponding thermodynamic properties (enthalpy and entropy changes) have been analyzed. The remarkable finding was that the transformation to 2H in the polycrystalline samples couldn’t go on completion. On the other hand, this behaviour was not observed for the transition to 18R, within the experimental scatter.