Two way shape memory effect in CuZnAl single crystals after pseudoelastic cycling at low temperatures

Abstract

CuZnAl alloys show pseudoelasticity, shape memory behavior and if adequately treated also the two way shape memory effect (TWSME), i.e., shape change due to the martensitic transition both during cooling and by heating. The origin of this phenomenon has been strongly discussed and the role that diffusion and dislocations play on the introduction of the TWSME has been and still is discussed in the literature. However many of the reported training or educational methods show the overlapping of dislocation generation and diffusion both in the austenite and in the martensite. This work deals with the introduction of the TWSME in CuZnAl single crystals by pseudoelastic cycling at temperatures low enough to disregard the contribution of diffusion, which influences the martensitic bcc-M18R transition at temperatures as low as room temperature in these alloys. The microstructure responsible for the introduction of the TWSME is discussed and the analysis of the effect of dislocation arrays, retained martensite, precipitates and microplasticity is presented.