Pseudoelastic fatigue and diffusive phenomena in Cu-Zn-A1 single crystals

Abstract
The mechanical behavior of the pseudoelastic cycles in CuZnA1 single crystals, at temperatures higher than room temperature, is affected by the occurrence of diffusive phenomena. Conversely, the diffusive phenomena are altered when defects are formed during cycling. In the present work we analyze the effects of pseudoelastic fatigue on the mechanical behavior. A critical step in the analysis is the definition of a reference state in order to quantify the further evolutions. Results show how this reference state depends on the test temperature, and in which way this fact must be considered if the mechanical evolution of the material is analyzed. Recently it has been shown how the characteristics of the diffusion related processes under static conditions are altered after cycling. In this work an upper limit temperature for this effect is presented. As an example, the stabilization of martensite under non dynamic conditions (static stabilization) was found to be significantly reduced after cycling at 333 K but shows no changes at 376 K. The range of temperatures at which this phenomena is present is then determined. The effect of the stabilization due to the equilibrium concentration of vacancies, and their interaction with bulk defects, is considered in order to improve the comprehension of different contributions to the mechanical behavior.