Effects of Different Zn/Mg Ratio and Ti Content on Hot Extruded 7xxx series Aluminum Alloy

The effects of alloy composition (Zn/Mg ratio and Ti content) on the microstructure and properties of Al–3.5Mg–xZn–1.22Cu–0.2Zr–yTi aluminum alloy were studied in this paper. The results show that after solution treatment at 450°C × 2h + 460°C × 2h + 470°C × 2h + 475°C × 2h, when the Zn/Mg ratio of the alloy increases from 3.55 to 3.85, the grain size of the alloy increases, the insoluble phase increases, the dislocation decreases, and the intergranular corrosion resistance decreases gradually. Under the condition of T6 aging, the hardness and electrical conductivity of the alloy decreased at first and then increased, and the compressive strength at room temperature also decreased at first and then increased, and the hardness and compressive strength reached the maximum when the Zn/Mg ratio was 3.85. When Zn/Mg is constant, with the increase of Ti content (0–0.88 wt %), the recrystallization degree of the alloy decreases, the insoluble phase increases, the dislocation density and strengthening value gradually decrease, the inter-granular corrosion resistance decreases gradually, and the hardness, electrical conductivity and compressive strength of the alloy decrease gradually under T6 aging.