Effect of Heterogeneous Lamellar Structure on Mechanical Properties and Electrochemical Corrosion Behavior of Al-Zn-Mg-Cu Alloy Subjected to High-Pressure Torsion

The heterogeneous lamellar structure composed of a mixture of coarse crystal layer and fine crystal layer can improve the mechanical properties and corrosion resistance of the metal. To obtain high-performance aluminum alloy with heterogeneous lamellar structure, high-pressure torsion experiments have been carried out at 360, 380 and 400 °C. The results of tensile test and electrochemical corrosion test show that the strength of the alloy increases from 682.46 to 781.03 MPa and the polarization resistance increases from 42.91 to 81.12 kΩ cm² with the increase in deformation temperature. It can be inferred from optical microscopy and transmission electron microscope observations that the strength of the alloy increases with increasing temperature. This is because the geometrically necessary dislocations at the interface increase during the stretching process, which in turn increases the back stress. Moreover, the enhancement of chemical corrosion resistance can be attributed to the decreased volume fraction of grain boundaries, which results in an increase in the compactness of the passivation film in the corrosive environment.