Effects of torsional cold work hardening on dynamic and static mechanical properties of 6061-T651 aluminum alloy

The 6061-T651 aluminum alloy was strengthened by torsional deformation with the torsion angles of 90°, 180° and 360°. The quasi-static and dynamic compressive properties of the samples before and after torsional deformation were investigated. The results show that the grain size of the samples remains unchanged at first with the increase of the torsion angle, and then begins to decrease. However, the Kernel average misorientation(KAM) value continues to increase with the increase of the torsion angle. The quasi-static and dynamic compression experiments show a slight increase in the yield strength of the samples with the increase of the torsion angle. For the same torsion angle, the dynamic yield strength is significantly higher than the yield strength at quasi-static loading. The strain rate experiment shows that the yield strength of the sample increases with the increase of strain rate, but compared with the untorsional sample, the strain rate sensitivity of the 360° torsional sample is significantly reduced. Based on the experimental data, the parameters in the Cowper-Symonds constitutive model were fitted. The stress-strain curves obtained from this model are in good agreement with the experimental results.