Nanostructure and mechanical properties of 0–7 strained aluminum by CGP: XRD, TEM and tensile test

Commercial purity aluminum sheets are subjected to a severe plastic deformation technique called constrained groove pressing. In this study for the first time by using some technical optimizations, a strain magnitude of 6.9 is imposed to the sheets. The grain size evolution during severe plastic deformation is studied using Williamson–Hall analysis on X-ray diffraction pattern of the deformed samples. These results and transmission electron microscopy observations show that constrained groove pressing process can effectively refine the coarse-grained structure to an ultrafine grain range. The results of mechanical tests show that imposing strain in range of 0–5.75 causes to strengthening of sheets, however imposing more strain reduces the strength and hardness of the sheets. Considering the hardness results and effect of specimen thinning before tensile test on yield stress and UTS, it is concluded that two mechanisms of micro-cracking and flow softening cause to observe a strength drop in the tensile test results of sheets with its original thickness. Also, the results show that the constrained groove pressing process causes to decrease of work hardening rate and increase of strain rate sensitivity of the sheets material.