Effect of three-stage homogenization on recrystallization and fatigue crack growth of 7020 aluminum alloy
Zhaojun Shan, Shengdan Liu, Lingying Ye, Xiaodong Liu, Yu Dong, Yiran Li, Jianguo Tang, Yunlai Deng, Xinming Zhang
Abstract
The effects of three-stage homogenization on recrystallization and fatigue crack growth behavior of 7020 aluminum alloy were investigated. It was shown that a large amount of fine Al3Zr dispersoids form in the grain and near the grain boundaries of the alloy after three-stage homogenization. The ratio of volume fraction to radius for the Al3Zr dispersoids after three-stage homogenization increased by 171.2% compared with the one-stage homogenization. The recrystallization fraction was reduced from 29.5% for the one-stage homogenized alloy to 19.1% for the three-stage homogenized alloy. If the fatigue crack propagation encounters small recrystallized grains with high misorientation, the crack is easy to grow quickly along grain boundaries. When the stress intensity factor at the crack tip is 10MPa·m1/2, the fatigue crack growth rate (FCGR) of the one-stage homogenized alloy is 30.6% faster than that of the three-stage homogenized alloy.