The effect of stacking fault energy on equilibrium grain size and tensile properties of ultrafine-grained Cu-Al-Zn alloys processed by rolling

Cu-2.5 at.% Al-2.5 at.% Zn, Cu-4.5 at.% Al-22.8 at.% Zn and Cu-12.1 at.% Al-4.1 at.% Zn alloys with stacking fault energies (SFEs) of 40, 10, and 7 mJ/m2, respectively, were processed by combination of room temperature rolling (RR) and liquid nitrogen temperature rolling (LNR). The effect of SFE on microstructure refinement and mechanical properties of these materials were investigated. Microstructural observations indicate that a decrease in SFE leads to a decrease in crystallite size and to increase in microstrain, dislocation and twin densities for the RR and LNR samples. The results show that under the same deformation conditions, lower SFE promotes the formation of nanostructures and deformation twins. An analysis shows that the experimental results are consistent with a theoretical model which predicted the minimum grain size produced by milling.