Studies of martensitic transformation in Cu-Al alloys by positron annihilation

The reverse martensitic transformations in Cu-23.5at-%Al, and Cu-25.3at-%Al have been studied by means of positron annihilation. The coincidence counting rates of angular correlation were measured as a function of the specimen temperature. The change of counting rates in heating run was rather different from that in cooling run due to the influence of tempering of martensitic structure. The results were interpreted by the change of the formation energy of a vacancy with phase transition. Influence of heating rate is also discussed.