The Effect of Pre-Deformation on the Microstructure and Hardness of Al-Zn-Mg-Cu Alloy

In this paper, hot rolling pre-deformation treatment was applied to an Al-Zn-Mg-Cu alloy after solid solution treatment, followed by peak aging treatment. The effect of the degree of deformation was discussed. The microstructure of the alloy after treatment was observed and the mechanical properties were tested. The results indicate that after hot rolling pre-deformation, high-density dislocations are introduced within the grains of the Al-Zn-Mg-Cu alloy, and the dislocation density gradually increases with the degree of deformation. At the same time, with the increase of rolling deformation, the alloy hardness first increases and then decreases. When the deformation is 40%, the alloy hardness reaches a peak value of 101.7 HV. In the subsequent aging process, with the increase of deformation, the time required to reach peak aging is gradually shortened, and at 40% deformation, the alloy hardness reaches a peak of 99.7 HV after 12 h of aging. Moreover, the dislocations generated by pre-deformation can become entangled around the grain boundary and the coarse quenching precipitated phase, providing nucleation particles for the subsequent precipitation of the strengthened phase, effectively improving the precipitation strengthening effect of the alloy during aging, and thus improving the hardness of the alloy at the peak aging state. This study provides a research idea for improving the hardness of the alloy and expands the application of the deformation aging process in Al-Zn-Mg-Cu alloys.