Effect of cryorolling and ageing on the microstructure and mechanical properties of Al 7085 alloy

Abstract

Cryorolling (CR) can effectively avoid room temperature rolling cracking of high-strength aluminum alloy. In this work, solution-treated bulk Al 7085 alloy samples were subjected to CR and room temperature rolling (RTR), respectively. When the deformation was 70%, the RTR sample was broken, while the CR one still had no cracks when the deformation was up to 90%. Consequently, the microstructure and mechanical properties of the CR samples before and after ageing treatment were investigated. The results show that after the solution-treated bulk Al 7085 alloy samples were cryorolled, the yield strength (YS) and the ultimate tensile strength (UTS) were increased by 74% and 31%, respectively. However, the elongation to failure (EtF) was decreased. After the subsequent 100 °C/20 h peak ageing (PA) treatment, the YS and UTS can be further increased by 14% and 10%, respectively, and the EtF was increased by 39% compared with that of the CR samples. After PA treatment, nanosized GP zones and η′ precipitates were precipitated. Precipitation strengthening is the main contributor to the strength enhancement of CR samples after PA treatment, which can not only compensate for the reduction caused by the decrease in dislocation density but also improve the strength of the material.